UC-NRLF 


31    fl?fl 


LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 


GIFT 


Class 


••••/*• 


heory  and  Practice 


OF 


PAINTING  ON  METAL 


BY 


A.    HL    SABIN,    M.   S. 


PUBLISHED    BY 

DWARD    SMITH    AND    COMPANY 

45     BROADWAY, 


Rusted  steel  plates;  upper  plate  cleaned,  lower  showing  "tubercles"  of  rust. 

(Frontispiece.) 


THEORY  AND  PRACTICE 


OF 


PAINTING    ON   METAL 


BY 

A.    H.    SABIN,    M.  S. 


PUBLISHED    BY 

EDWARD    SMITH  AND  COMPANY 
45    BROADWAY,    N.   Y. 


Copyright,  1905, 

BY 
EDWARD  SMITH  AND  COMPANY 


THEORY    AND    PRACTICE    OF    PAINTING 

ON    METAL 


i. 

IN  1898  the  writer  put  out  a  little  book  of  specifications  for 
painting  on  structural  metal,  which  has  been  received  with  con- 
siderable favor;  but  the  last  edition  (of  two)  is  now  out  of  print 
and  it  has  seemed  desirable  to  reprint  the  specifications  and 
to  add  such  remarks  as  further  experience  has  suggested.  The 
specifications  themselves  are  almost  unchanged;  but  some  work 
has  recently  been  done  which  exceeds  in  excellence  and  thorough- 
ness anything  heretofore  described,  and  it  seems  well  to  give^a 
somewhat  detailed  account  of  it,  which  will  be  done  in  proper 
course. 

Uncombined  metallic  iron  is  so  rare,  as  a  natural  mineral, 
that  practically  there  is  no  such  thing.  It  is  found  chiefly  as  an 
oxide,  though  carbonates,  silicates,  and  other  salts  abound  and 
in  particular  the  sulphide,  pyrite,  is  very  widely  distributed.  It 
may  be  said  that  the  coloring-matter  of  most  of  the  dark-colored 
minerals  and  rocks  is  mainly  iron.  Metallic  iron  is  obtained 
from  the  ore  by  using  the  most  powerful  chemical  agencies  and 
it  constantly  tends  to  go  back  into  combination;  when  it  does 
this  by  natural  means  the  product  is  termed  rust.  Usually  rust 
is  hydrated  oxide  of  iron,  mixed  with  more  or  less  carbonate,  and 
often  with  sulphate,  sulphide,  chloride,  or  other  salts  of  iron. 
The  common  cause  of  rust  is  the  action  of  air  containing  moisture 
and  acids,  especially  carbonic  acid;  and  to  prevent  it  we  must 
exclude  water  and  gases.  This  is  very  difficult,  but  has  been 
attempted  in  many  ways. 

5 


In  the  first  place,  by  embedding  the  metal  in  cement.  Bridge 
floors  are  sometimes  covered  with  melted  asphaltum  an  inch 
or  more  in  thickness;  a  good  result  may  thus  be  obtained,  but 
as  the  material  is  of  a  viscous  nature  and  tends  to  flow  slowly 
off  a  surface  not  level  and  confined,  it  is  of  limited  application. 

Of  far  greater  use  is  Portland 
cement,  or  concrete  made  of  it; 
this  is  strongly  alkaline,  not 
only  with  caustic  lime,  but  the 
action  of  this  on  the  potassium 
and  sodium  compounds  origi- 
nally present  in  the  clay  from 
which  the  cement  is  made  sets 
free  caustic  potash  and  soda. 
These  strongly  alkaline  bodies 
naturally  prevent  the  access  of 
acids  and  thus  prevent  rust- 
ing. The  best  Portland-cement 
mortar  is  somewhat  porous; 
and  concrete  is  liable  to  con- 
tain voids,  which  increase  its 
permeability;  cracks  often  oc- 
cur, and  it  is  known  to  be 
exceedingly  difficult  to  make 
concrete  even  approximately 
water-tight.  Whether  steel 
which  is  to  be  embedded  in 
concrete  should  or  should  not 
be  painted  is  a  question  about 
which  there  is  no  sort  of  agree- 
ment. On  one  side  it  is  said 
that  cement  naturally  forms  a 
strong  bond  with  a  metallic  iron 
surface,  and  that  even  if  it  is 
a  little  rusty  this  rust  will  be 
taken  up  by  the  cement.  The 
recent  and  apparently  careful 
tests  by  Breullie  appear  to  show 
that  there \  is;  considerable  ad- 
hesion between  Portland-cement  mortar  and  steel  or  iron  surfaces, 
and  that  this  adhesion  is  determined  by  chemical  action ;  also  that 
the  compound  thus  formed  is  soluble  in  water,  that  if  it  be  removed 
by  percolation  the  bond  is  destroyed,  and  "that  when  it  becomes 

6 


Stand-pipe  at  Racine,  Wis.,  135  ft. 
high.  Steel  tank  painted  with 
Durable  Metal  Coating.  W.  H. 
Laing,  Supt. 


necessary  to  rely  upon  this  bond  to  preserve  the  integrity"  of 
any  composite  structure  "which  is  exposed  to  the  action  of  water, 
it  becomes  necessary  to  make  the  concrete  impervious  to  water." 
(Eng.  News,  Vol.  LI,  pp.  561,  562.) 

M.  Breullie  made  also  a  series  of  experiments  to  determine 
the  strength  of  this  bond  existing  between  mortar  composed  of 
.1  part  cement  to  2  parts  sand  and  iron.  His  conclusion  was  that 
after  30  days  it  amounted  to  22  pounds  per  square  inch  of  sur- 
face. When  we  consider  that  this  is  only  10  per  cent  of  the 
strength  of  the  concrete  and  a  twentieth  of  i  per  cent  of  the 
strength  of  the  steel,  it  seems  of  very  doubtful  value;  and  the 
almost  universal  practice  of  using  twisted  bars,  or  those  rolled 
in  irregular  shapes  so  as  to  make  anchorages,  which  utilize  the 
rigidity  of  the  cement,  seems  fully  justified.  Metal  wliich  is 
embedded  in  concrete  is,  however,  strongly  held  in  place  by  the 
pressure  against  it,  caused  by  the  shrinkage  of  the  cement  in  the 
act  of  setting,  provided  the  concrete  sets  in  air;  if  it  sets  under 
water  it  expands.  Metal  which  is  painted  will  be  gripped  in 
this  way  quite  as  well  as  that  which  is  unpainted;  and  if  the 
action  of  percolating  water  is  liable  to  cause  rusting  a  coat  of 
paint  ought  to  have  a  good  effect.  The  whole  matter  has  not 
been  sufficiently  studied;  but  M.  Breullie's  experiments  certainly 
seem  to  show  that  the  claims  made  for  the  existence  of  a  chem- 
ical "bond"  of  high  efficiency  between  concrete  and  metal  are 
extravagant  and  not  founded  on  measurements. 

In  any  case  only  a  small  percentage  of  structural  steel  can 
ever  be  embedded  in  concrete.  It  has  been  proposed  to  paint 
iron  with  a  cement  wash;  but  this  is  brittle,  and,  so  far  as  my 
own  observation  has  gone,  does  not  adhere  well.  Newberry 
says  that  in  order  to  have  it  adhere  well  it  should  be  kept  moist 
for  a  day  or  two,  which  is  manifestly  difficult.  We  come,  then, 
to  the  use  of  films  of  paint  and  varnish  to  prevent  the  action  of 
moisture  and  air. 

Ordinary  oil  paint  is  composed  of  linseed-oil  as  the  principal 
liquid  ingredient,  with  which  is  mixed  some  pigment;  which 
latter  is  a  solid  substance  very  finely  powdered.  The  pigments 
in  principal  use  for  the  protection  of  metal  are  white  and  red 
lead,  the  former  more  or  less  mixed  with  barytes  and  sulphate 
of  lime  and  sometimes  with  the  carbonates  of  baryta  and  lime,  the 
latter  with  iron  oxides,  graphite ,'boneblack,  and  lampblack;  with 
these  are  mixed  chrome  yellow,  chrome  green,  and  ochre  as  tinting 
materials.  The  lead  pigments  and  lampblack  are  in  their  nature 
chemical  precipitates,  and  are  extremely  fine;  but  the  others 

7 


are  for  the  most  part  pulverized  by  grinding;  and  it  is  a  general 
opinion  that  a  given  pigment  is  better  the  finer  it  is.  Experiments 
in  regard  to  the  amount  of  pigment  required  are  not  in  accord 
with  each  other;  at  one  time  it  was  commonly  believed  that 
the  greater  the  proportion  by  weight  of  pigment  the  better  was 
the  paint ;  now  it  is  claimed  that  the  finer  the  pigment  the  better ; 
but  the  finer  the  pigment  the  smaller  is  the  proportion  which 
can  be  mixed  with  :the  oil,  so  far  as  weight  is  concerned.  The 
fact  probably  is,  that  the  greater  the  number  of  particles  of  pig- 
ment in  a  given  measure  of  paint  the  better  it  is,  or  else  that 

the  greater  the  aggregate  surface  of 
these  particles  the  better;  the  latter  is 
the  more  likely  to  prove  correct,  and 
would  make  reasonable  allowance  for 
the  relatively  coarse  condition  of  graph- 
ite, which  cannot  commercially  be 
ground  to  an  extreme  degree  of  fineness, 
but  which  is  in  thin  flakes,  presenting 
a  large  amount  of  surface. 

The  use  of  pigment  in  a  paint  is 
threefold:  it  makes  liquid  paint  thicker 
than  oil  and  thus  causes  a  thicker  film 
to  adhere  to  the  surface;  being  com- 
posed of  solid  particles,  it  hardens  the 
film  and  thus  enables  it  to  resist  abra- 
sion; and  the  particles  of  pigment  fill 
up  many  of  the  pores  in  the  oil  film 
and  so  make  it  more  impervious  to  air 
and  moisture.  The  use  of  the  oil,  on 
the  other  hand,  is  to  form  a  water-proof 
coating  as  impervious  as  may  be  to  gases 
as  well  as  liquids,  and  to  act  as  a  cement- 
ing material  or  binder,  to  hold  together 
the  particles  of  pigment  and  attach  them 
to  the  surface.  The  best  oil  for  this  pur- 
pose is  probably  linseed  w  ich  differs  from  almost  all  other  oils  in 
the  fact  that  when  it  is  exposed  to  the  air  it  is  converted  into 
a  dry,  tough,  leathery,  or  rubber-like  substance  known  as  linoxyn. 
This  change  is  caused  by  chemical  action;  the  oil  absorbs  and 
unites  with  oxygen,  which  it  takes  from  the  air,  and  so  increases 
in  weight;  it  dries,  but  not  in  the  way  a  watery  solution  does. 
The  film  thus  formed  is  not  entirely  impel  vious ;  it  is  quite  insolu- 
ble in  water,  dilute  acids,  and  all  ordinary  solvents;  but  it  is 

8 


Stand-pipe  at  Sedalia,  Mo., 
of  the  M.  K.  &  T.  R.R. 
S.  B.  Fisher,  Cons.  Eng. 
Painted  with  Durable 
Metal  Coating. 


somewhat  porous.  The  supposition  has  been  advanced  that  it 
absorbs  oxygen,  combines  with  it  to  form  carbonic  acid,  and 
that  the  escape  of  this  gas  causes  the  formation  of  holes,  or  pores; 
this  seems  unlikely,  because  if  this  action  took  place  it  would 
be  a  true  .combustion  and  would  be  accompanied  by  a  loss  of 
weight;  on  the  contrary,  it  increases  in  weight;  the  increase 
being  stated  by  Livache  at  16  to  18  per  cent  and  by  Andes  at 
14  to  19.7  per  cent.  Further,  if  the  pores  in  an  oil  film  were  blow- 
holes it  is  difficult  to  see  how  the  particles  of  pigment  would 
close  them;  the  latter  would  be  pushed  out  of  the  way;  but 
in  fact  nothing  is  better  established  than  that  the  porosity  of 
the  film  is  greatly  diminished  by  the  presence  of  pigment.  The 
cause,  then,  of  the  porosity  of  a  paint  film  must  be  sought  in 
some  other  way. 

Let  us  look  at  it  in  this  way.  A  gallon  measures  231.  cubic 
inches.  Spread  over  400  square  feet  of  surface  this  would  make 
a  layer  .004  of  an  inch  in  thickness.  Now,  I  have  measured  with 
a  micrometer-caliper  a  great  many  dry  films,  and  two  coats  of 
dry  paint  seldom  measure  more  than  .004  and  the  most  I  have 
ever  seen  was  .006;  these  were  on  test-plates,  where  care  was 
taken  to  lay  on  full  heavy  coats,  and  the  proportion  of  400  square 
feet  to  the  gallon  (which  is  more  than  the  average  of  commer- 
cial work  in  painting  on  iron)  could  hardly  have  been  exceeded. 
Hence  it  appears  that  the  film  shrinks  from  30  to  50  per  cent 
in  bulk.  This  means  also  that  the  specific  gravity  of  the  oil 
increases,  which  is  the  fact;  I  have  never  been  able  to  oxidize 
linseed-oil  without  its  containing  air-bubbles,  but  notwithstand- 
ing this  the  oxidized  oil  is  heavier  than  water;  so  it  may  be 
regarded  as  certain  that  considerable  shrinkage  in  volume  takes 
place.  When  an  oil  film  dries  it  turns  first  to  a  gelatinous  sub- 
stance, or  becomes  tacky;  this  doubtless  prevents  its  flowing; 
and  then  as  it  shrinks,  the  contraction  causes  pores  to  form  in 
the  film,  which  is  drawn  apart  into  a  sort  of  network,  differing 
from  an  ordinary  network  in  that  the  openings  occupy  less  area 
than  the  solid  portions.  The  smallest  of  these  pores  probably 
do  not  let  water  pass  through,  unless  under  pressure,  because 
of  their  capillary  action;  but  it  enters  some  of  the  larger  ones. 
If  the  oil  is  mixed  with  particles  of  pigment,  which  do  not  con- 
tract, we  would  naturally  expect  these  to  stop  up  many  of  these 
holes  in  the  film,  and  that  is  certainly  what  takes  place.  This 
explanation  is  simple  and  reasonable,  agreeing  with  all  the 
facts. 

Supposing  this  explanation  of  the  lack  of  continuity  of  a 

9 


paint  film  to  be  the  true  one,  as  I  believe  it  to  be,  we  may  next 
consider  other  means  of  making  a  less  porous  coating. 

Films  which  are  approximately  water-proof  may  be  made  of 


Stand-pipe  at   Lawrence,   Mass.     Steel  tank  painted   with    Durable 
Metal  Coating. 

varnish.  The  most  durable  varnishes  are  those  which  have 
linseed-oil  as  their  elastic  ingredient,  with  which  is  united  a  pro- 
portion of  resinous  matter.  Coatings  of  this  nature  have  been 
known  from  very  remote  times;  the  exterior  wrappings  of  the 
Egyptian  mummies  were  varnished,  and  the  wooden  boxes,  or 
mummy-cases,  in  which  they  were  laid,  were  thoroughly  pro- 
tected with  thick  coats  of  what  undoubtedly  is  an  oleo-resinous 
varnish,  which  is  still  in  good  condition,  twenty-five  centuries 
after  its  application;  it  may  be  seen  in  any  of  the  large  museums 
of  antiquities.  No  oil-paint  has  ever  shown  such  durability. 
It  is  no  new  thing  to  use  such  varnish  as  a  preservative  on  iron. 
In  a  manuscript  of  the  date  of  1520,  in  the  library  of  San  Marco 
in  Venice,  is  a  recipe  for  varnish  for  iron  armor  consisting  of 
two  pounds  of  linseed-oil  to  i  pound  of  a  varnish  resin;  another 
author,  Mathioli,  in  1549  said  that  "with  resin  and  linseed-oil  is 
prepared  the  liquid  varnish  which  is  used  for  giving  lustre  to 
pictures  and  for  varnishing  iron";  and  a  Venetian  author,  Cane- 

10 


parius,  in  1619  said  that  with  resin  and  linseed-oil  is  made  a  var- 
nish which  "adds  splendor  to  iron  and  preserves  it  from  rust." 
Similar  instances  may  be  quoted  down  to  the  present  time;  this 
use  of  varnish  has  been  more  common  in  Europe  than  in  this 
country;  for  example,  the  Eiffel  tower  was  painted,  when  it 
was  built, -with  a  paint  in  which  an  oleo-resinous  varnish,  not 
oil,  was  the  liquid  with  which  the  pigment  was  mixed.  But  it 
is  not  unknown  here ;  the  author  has  made  oleo-resinous  varnishes 
for  painting  hundreds  of  bridges  and  other  important  structures, 
with  the  most  successful  results.  It  is,  then,  worth  while  to 
inquire  into  the  nature  of  these  preparations.  The  resins  from 
which' varnish  is  made  are  of  vegetable  origin;  but  in  most  cases 


Stand-pipe,  Framingham  Water  Co.,  South  Framingham,  Mass.  Height,  81 
feet;  diameter,  40  feet;  capacity,  750,000  gallons.  This  stand-pipe  is 
coated  with  Durable  Metal  Coating. 

they  are  fossil  or  semi -fossil  resins,  which  after  the  fall  and  decay 
of  the  trees  by  which  they  were  produced,  have  laid  buried  in 
the  earth  for  a  long  time,  in  some  cases  hundreds  or  even  thou- 

1 1 


sands  of  years;  during  which  time  they  have  hardened  and 
have  lost  their  perishable  ingredients.  To  make  varnish,  a 
quantity  of  some  of  these  resins  is  melted  in  a  suitable  vessel; 
to  this  is  added  a  proper  amount  of  hot  linseed-oil,  and  the  mix- 
ture is  then  heated  for  some  hours  until  the  ingredients  have 
thoroughly  combined.  It  is  then  thinned  with  spirit  of  tur- 
pentine until  its  consistency  is  such  that  when  cold  it  will  be 
suitable  for  use.  When  this  liquid  is  spread  out  in  a  thin  film 
it  has  the  quality  of  hardening,  as  linseed-oil  does,  by  the  absorp- 
tion of  oxygen  from  the  air,  and  is  converted  into  a  coating  which 
is  harder,  smoother,  and  less  porous  than  an  oil  film.  It  is  natu- 
ral to  expect  that  it  will  be  harder,  because  the  resin  which  has 
been  added  to  the  oil  is  harder  than  the  dried  oil ;  but  why  should 
it  be  smoother  and  less  porous? 

Nearly  every  one  is  familiar  with  the  common  use  of  rosin 
for  soldering;  where,  being  melted,  it  acts  as  a  flux,  dissolving 
and  carrying  away  the  solid  particles  or  film  of  metallic  oxides 
which  would  otherwise  prevent  the  contact  of  the  solder  with 
the  metal.  All  resins  appear  to  be  able  to  act  as  fluxes;  and 
when  dissolved  in  oil  they  act  in  such  a  way  as  to  make  a  com- 
pound which,  instead  of  being  a  stiff  jelly  which  breaks  up  on 
contraction  into  a  network  of  holes,  remains  until  it  is  dry  (or 
nearly  so)  a  continuous,  sticky,  elastic  film,  nearly  free  from 
porosity;  and  while  the  surface  of  an  oil  film  is  corrugated  by 
countless  minute  wrinkles,  a  varnish  makes  a  smooth  surface; 
not  only  is  this  smoothness  characteristic  of  the  surface,  but  it 
is  indicative  of  the  nature  of  the  film  throughout  its  whole  thick- 
ness; the  film  is  continuous  and  of  uniform  structure.  At  least 
it  appears  to  be  so,  and  that' is  the  general  belief;  but  probably 
at  the  very  last  some  pores  are  formed,  for  such  films,  though 
far  less  porous  than  oil  films,  do  not  form  an  absolutely  perfect 
protection,  but  are  more  satisfactory  than  any  other  coating 
which  dries  in  the  ordinary  way. 

All  good  varnishes  have  this  nature;  but  not  all  good  var- 
nishes are  suitable  for  the  protection  of  structural  metal;  because 
if  the  proportion  of  resin  is  too  large  the  varnish  is  so  hard  that 
it  is  deficient  in  toughness,  and  cracks  from  sudden  changes  of 
temperature. 

It  is  impossible  to  have  a  surface  too  hard,  if  it  is  not  brittle; 
but  it  is  absolutely  necessary  to  have  it  tough.  The  larger  the 
proportion  of  resin  the  more  brilliant  is  the  varnish;  and  for 
most  purposes,  that  is,  where  varnish  is  regarded  as  an  adorn- 
ment as  well  as  a  protective  material,  it  is  desirable  to  have  a 

12 


high  degree  of  brilliancy;  moreover,  there  are  many  places,  as 
for  example  the  outside  of  a  railway  coach,  where  the  surface 
is  subjected  to  constant  abrasion,  where  a  considerable  degree 
of  hardness  must  be  had  at  any  cost,  even  though  a  sacrifice 
of  elasticity  and  toughness  result.  So  it  is  that  all  ordinary 
varnishes  are  deficient  in  this  respect;  and  a  varnish  particu- 
larly designed  for  protective  rather  than  decorative  effect  must 
be  made  of  somewhat  different  materials  and  in  a  somewhat 
different  way  from  those  in  ordinary  use.  Up  to  a  certain  point, 
the  larger  the  proportion  of  oil  in  a  varnish  the  tougher  and  more 
durable  it  is;  but  if  more  oil  is  put  in  than  can  properly  com- 
bine with  the  resinous  matter  it  acts  as  a  mixture,  and  then  the 
film  begins  to  lose  the  characteristics  of  a  varnish  coating  and  to 
resemble  an  oil  film.  This  proportion  cannot  be  definitely  stated,  as 
it  varies  according  to  the  character  of  the  resin  used  (of  which  there 
are  many  kinds) ,  and  to  some  extent  with  the  details  of  the  process 
of  varnish-making,  in  which  practical  men  differ  considerably. 

It  is  often  said  that  as  any  true  oleo-resinous  varnish  is,  when 
dry,  harder  than  oxidized  oil,  it  is  therefore  less  elastic.  No 
doubt  a  varnish  may  be  made  with  so  great  a  proportion  of  resin 
as  to  be  lacking  in  elasticity,  but  it  must  be  remembered  that 
flexibility  and  elasticity  are  essentially  different  things;  and 
while  an  oil  film  may  be  softer  and  more  flexible,  it  may  at  the 
same  time  be  less  elastic  than  a  varnish  film;  and  this  is  cer- 
tainly true.  Steel  is  probably  less  flexible  than  lead,  but  it  is 
more  elastic,  and  wears  better;  and  a  baked  varnish  enamel 
may  be  made  which  is  far  harder  than  any  ordinary  varnish  film, 
while  it  surpasses  oil  in  toughness  and  is  greatly  superior  to  either 
in  freedom  from  porosity  and  in  durability  under  all  conditions. 
So  it  is  clear  that  hardness  in  a  film  is  not  necessarily  an  objec- 
tion, but  it  is  in  part  a  desirable  quality.  It  will  be  remembered 
that  the  three  objects  for  which  we  add  pigment  to  oil  are  to 
get  a  thicker,  harder,  and  less  porous  film;  varnish  makes  a  film 
which  is  harder  and  less  porous;  but  how  about  thickness?  To 
this  it  may  be  said  that  pigment  adds  to  the  thickness  of  an  oil 
film  by  making  the  liquid  paint  thicker  or  more  viscid  than  oil 
alone;  but  varnish  is  in  its  nature  more  viscid  than  oil,  hence 
it  may  be  laid  on  in  a  thick  coating.  It  is  reasonable,  then,  to 
expect  that  a  varnish — not  any  varnish,  but  a  special  varnish 
made  of  the  most  suitable  materials  and  with  proper  knowledge — 
will  be  more  durable  than  an  oil-paint;  it  is  smoother,  tougher, 
less  liable  to  be  affected  by  chemical  action,  and  more  homo- 
geneous. Such  we  believe  to  be  the  fact. 


Practical  experience  supports  this  belief.  The  writer  has 
recently  inspected  an  important  bridge  of  considerable  size — 
two  plate-girder  spans  of  100  feet  each — which  is  subjected  to 
refrigerator  drip,  and  over  which  fifty  trains  pass  daily,  which 
has  not  had  any  repainting  since  it  was  built,  more  than  ten 
years  ago;  and  was  unable  to  find  any  rust  on  it,  or  any  sen- 
sible deterioration  of  the  varnish,  with  two  coats  of  which  it 
was  originally  coated.  Another  bridge  which  had  a  similar  pro- 


Steel   stand-pipe,  Winchester,  Mass.      Height,  40    feet;   diameter,  40   feet. 
This  stand-pipe  is  coated  with  Durable  Metal  Coating. 

tection  has  a  draw  500  feet  long;  it  is  over  sea-water,  and  tugs 
pass  under  it  continually;  this  was  badly  rusted  in  1895  and 
was  then  repainted ;  in  the  opinion  of  the  writer  it  needs  repaint- 
ing now,  after  nine  years,  but  such  is  not  the  judgment  of  the 
inspecting  engineer,  so  it  may  be  conceded  that  the  treatment 
has  proved  exceptionally  satisfactory.  It  is  not  possible  to  get 
as  good  results  on  an  old  and  rusty  structure  as  on  a  new  one, 
and  the  situation  is  a  hard  one  as  regards  corrosion.  In  Chicago 
there  are  a  number  of  viaduct  bridges  about  1600  feet  long,  over 


railroad  tracks,  which  were  coated  with  this  same  varnish,  one 
coat  at  the  shop  and  one  coat  after  erection,  in  1895  an(i  1896, 
and  have  not  yet  needed  any  further  care;  and  one  of  the  large 
train-sheds  in  that  city  has  been  efficiently  protected  in  the  same 
way  nearly  as  long.  Scores  of  railway  bridges  can  be  seen  which 
have  stood  eight  to  ten  years  with  nothing  on  them  but  the  var- 
nish with  which  they  were  originally  coated;  and  in  Boston  may 
be  seen  the  great  highway  bridge  connecting  that  city  with  Charles- 
town,  a  structure  protected  in  part  with  varnish  and  the  remainder 
with  a  varnish  enamel  paint,  which  has  stood  more  than  five 
and  in  part  more  than  six  years;  not  so  much  as  a  rivet-head 
has  been  repainted,  and  the  surface  is  in  fine  condition.  The 
anchorages  of  the  Williamsburg  bridge,  the  greatest  suspension 
bridge  in  the  world,  which  connects  New  York  and  Brooklyn, 
were  protected  only  with  varnish;  and  the  cables  and  steel  floor 
of  the  same  bridge  were  treated  with  special  compounds  of  the 
same  general  nature,  which  will  be  described  later. 

It  is  not  enough  to  use  the  best  kind  of  a  protective  coating; 
it  must  be  properly  applied.  The  first  thing  to  be  considered 
is  the  preparation  of  the  surface;  it  makes  no  difference  whether 
the  coating  is  for  protective  or  decorative  effect,  whether  it  is 
a  piano,  a  carriage,  the  outside  or  inside  of  a  house,  a  train-shed, 
or  a  railway  bridge;  whether  it  be  wood,  tin,  iron,  or  steel;  the 
original  surface  must  first  be  put  in  proper  condition,  or  the 
money  spent  on  it  will  be  likely  to  be  wasted,  at  least  in  part. 
There  are  people  who  think  that  paint  forms  an  impervious  coating, 
and  will  therefore  arrest  any  changes  which  may  be  going  on 
where  it  is  applied;  but  none  of  those  people  are  in  the  paint 
business.  The  belief  is  absolutely  universal  among  all  those  who 
are  making  a  living  from  the  use  of  paint  and  varnish,  that  no 
good  results  should  be  expected  where  the  surface  has  not  been 
properly  prepared;  it  may  fairly  be  assumed,  therefore,  that 
this  belief  is  founded  on  knowledge,  and  the  opposite  belief  on 
ignorance,  of  the  subject.  It  is  the  custom  of  those  who  apply 
surfacing  coatings  to  carriages,  articles  of  furniture,  and  the  like, 
first,  to  have  the  article,  if  a  wooden  one,  made  as  dry  and  clean 
as  possible;  then  to  fill  the  pores  of  the  wood  with  a  suitable 
material,  and  rub  it  to  a  smooth  surface  with  sandpaper  or  other 
abrasive  agent,  before  the  application  of  the  paint  or  varnish. 
In  a  much  cheaper  class  of  work,  exterior  house-painting,  the 
surface  is  made  clean  and  dry,  and  the  pores  are  filled  with  oil 
or  some  mixture,  before  painting;  and  painting  is  done  only  in 
dry  and  warm  weather.  Metallic  objects  are  coated  in  a  variety 

15 


of  ways;  some  receive  a  superficial  layer  of  tin  or  zinc  by  im- 
mersing them  in  a  bath  of  the  melted  metal;  some  have  a  nickel 
or  silver  layer  electrically  deposited;  some  are  coated  with  a 
vitreous  enamel;  and  still  others  are  dipped  in  a  special  sort  of 
varnish  and  then  this  is  hardened  by  baking  in  an  oven;  this 
latter  process  is  called  japanning.  But  in  all  these  cases  it  is 
regarded  as  absolutely  necessary  to  clean  off  all  the  dirt,  and 
even  to  remove,  by  the  action  of  acid  or  by  the  sand-blast,  abso- 
lutely all  the  oxide  and  scale,  so  as  to  show  in  all  parts  the  color 
of  the  pure  metal,  before  anything  else  is  done.  If  this  precau- 
tion is  not  observed,  experience  has  shown  that  the  coating  will 
not  adhere  properly;  either  it  is  easily  scraped  off,  or  if  more 
adherent,  the  difference  of  expansion  causes  it  to  flake  off  later. 
If  such  is  the  case  with  so  perfect  a  protective  material  as  elec- 
troplate or  enamel,  how  can  we  expect  it  to  be  otherwise  with 
a  much  less  completely  impervious  substance,  such  as  paint? 
There  can  be  no  doubt  that  the  right  way  to  paint  structural 
metal  is  to  apply  the  paint,  not  to  a  superficial  layer  of  dirt  or 
oxide,  but  to  the  pure,  clean  surface  of  the  metal  itself.  This 
can  be  done;  the  metal  may  be  made  perfectly  clean,  either  by 
the  use  of  the  sand-blast  or  by  pickling  with  dilute  acid,  details 
of  which  treatment  will  be  found  among  the  following  specifica- 
tions. 

Sometimes  it  is  not  practicable  to  have  the  metal  cleaned  in 
this  thorough  manner;  it  is  therefore  of  interest  to  consider  what 
are  the  most  and  what  the  least  objectionable  among  the  things 
which  obscure  its  surface.  Grease  and  mud  are  the  worst,  for 
paint  does  not  adhere  to  them  at  all;  then  comes  a  thick,  recently 
formed  layer  of  ordinary  rust.  This  is  composed  chiefly  of  the 
hydrated  oxide  of  iron;  but  it  always  contains,  even  though  it 
appears  dry,  moisture  held  in  it  as  in  a  sponge,  and  with  the 
water  carbonic  acid;  and  these,  imprisoned  beneath  a  layer  of 
^paint,  soon  assert  their  independence  and  regain  their  liberty. 
Such  a  coating  of  rust  is  itself  a  cause  of  chemical  action ;  it  is  in 
the  most  intimate  contact  with  the  unoxidized  metal,  to  which 
it  gives  up  a  part  of  its  oxygen,  quickly  regaining  from  the  external 
atmosphere  an  equivalent  amount;  in  this  way  it  is  a  carrier  of 
oxygen  between  the  air  and  the  pure  metal,  and  so  it  is  that  "  rust 
doth  corrupt."  There  can  be  no  safety  until  such  rust  is  removed; 
there  should  be  no  toleration  of  it. 

Of  quite  another  nature  is  the  black,  blue,  or  iridescent  mill- 
scale  which  is  formed  on  the  red-hot  iron  at  the  mill.  This  is 
also  an  oxide,  but  is  anhydrous,  being  either  the  magnetic  or, 

16 


more  commonly,  the  anhydrous  sesquioxide,  equivalent  to  the 
mineral  hematite;  and  the  principal  objection  to  painting  over 
it  is  that  its  attachment  to  the  underlying  metal  is  not  as  per- 
manent as  could  be  desired.  Its  rate  of  expansion  is  somewhat 
different,  and  if  this  causes  it  to  come  off  the  superimposed  coat- 
ing comes  off  with  it.  It  is  usual  for  it  to  consist  of  more  than 
one  layer,  and  sometimes  of  several;  in  which  case  the  outer 
part  easily  scales  off  from  the  inner.  This  anhydrous  oxide  is 
insoluble  in  acid;  often  the  film  next  the  metal  is  very  thin,  and 
instead  of  peeling  off  on  account  of  the  unequal  expansion,  it 
breaks  up  by  microscopic  cracks  into  pieces  so  small  that  they 
are  able  to  yield  to  small  stresses  caused  by  changes  of  tempera- 
ture; such  a  surface  is  very  satisfactory  for  painting,  provided 
it  is  taken  in  time,  before  rust  has  begun.  The  manner  in  which 
this  kind  of  scale  is  thrown  off  by  chemical  action  is  seen  when 
we  put  it  in  acid;  the  latter  penetrates  the  minute  cracks  and 
works  its  way  under  the  bits  of  scale,  which  are  thus  loosened 
and  removed. 

This  suggests  the  treatment  which  should  be  given;  all  loose 
scale  should  be  removed  by  mechanical  means  and  painting  should 
be  done  at  once.  Every  one  knows  of  the  permanence  of  paint 
marks  put  on  at  the  mill  while  the  metal  is  still  hot;  the  paint 
is  melted  into  a  sort  of  enamel  and  air  and  moisture  never  get  a 
chance  to  attack  the  metal.  If  the  latter  is  partially  cooled 
by  a  spray  of  water,  as  is  a  common  practice,  and  is  then  passed 
through  bending  or  straightening  rolls,  most  of  the  detachable 
scale  is  removed.  In  England  it  has  been  for  many  years  a  prac- 
tice to  coat  the  hot  metal  at  this  time,  that  is  at  a  black  heat, 
with  a  thin  film  of  oil,  which  bakes  on  by  the  residual  heat  in 
the  metal;  this  is  done  to  steel  rails  and  other  metal  work  which 
is  to  be  sent  on  a  long  sea  voyage,  as  to  India  or  Australia,  and 
is  found  an  efficient  temporary  protection  against  rust.  It  might 
be  an  excellent  first  coat,  preliminary  to  painting,  on  ordinary 
structural  metal;  the  film  is  thin,  but  hard  and  smooth;  if  desired, 
it  might  perhaps  be  made  of  a  sort  of  varnish,  and  be  somewhat 
thicker. 

The  floor  of  the  driveways  of  the  Williamsburg  bridge  is  paved 
with  wooden  blocks  which  rest  on  an  underfloor  composed  of 
steel  channels,  12  inches  wide  and  about  20  feet  long,  which  are 
laid  side  by  side  like  a  plank  floor.  These  channels  were  sent 
from  the  shop  to  an  enamelling-plant ;  when  received  there  they 
were  covered  with  shop-grease  and  dirt,  and  were  first  put  into 
a  tank  containing  a  hot  10  per  cent  solution  of  caustic  soda,  to 

17 


clean  them.  Next  they  were  dipped  in  a  tank  of  boiling  water; 
then  in  hot  10  per  cent  sulphuric  acid;  rinsed  again  in  hot  water, 
then  put  in  a  hot  10  per  cent  solution  of  carbonate  of  soda,  to 


Laying   the   steel    underfloor    (coated    with  Sabin  :  Pipe   Coating)    on   the 
Williamsburg  Bridge,  N.  Y.  City. 

remove  all  traces  of  acid,  again  rinsed  in  hot  water,  dried  in  an 
oven,  then  dipped  in  a  tank  of  hot  varnish  enamel,  removed, 
drained,  put  in  an  oven  and  baked  at  about  400°  F.  until  the 
coating  was  hard.  They  were  then  taken  out  and  allowed  to 
cool,  and  were'^shipped  to  the  bridge.  When  laid  in  place  there 
was  not  a  scratch  to  be  seen  on  more  than  one  piece  in  fifty;  and 
after  they  were  in  place  it  was  two  or  three  weeks  before  they 
were  protected  by  the  block  pavement,  during  which  time  the 
force  of  employees,  numbering  six  or  eight  hundred,  walked  to 
and  fro  on  them,  with  wheelbarrows,  casks  of  bolts,  and  the  like; 
and  at  the  end  of  this  time  the  coating  showed  practically  no 
injury.  This  was  observed  not  only  by  the  bridge  engineers, 
but  by  visiting  engineers  from  all  parts,  and  was  greatly  admired. 
The  sidewalks  also  have  a  steel  underfloor,  which  was  coated 
in  the  same  way.  This  was  probably  the  first  structural  metal 
(except  pipe)  which  was  ever  enamelled,  and,  with  the  exception 
of  the  metal  in  the  anchorages  of  the  old  Brooklyn  bridge,  is 

18 


believed  to  be  the  first  structural  metal  to  be  cleaned  by  pickling 
in  the  United  States.  Structural  work  has  been  sand-blasted 
here,  and  has  been  pickled  in  Europe  for  many  years.  This 
work  I  regard  as  the  most  thorough  and  perfect  in  the  way  of 
protection  agains.t  corrosion  which  has  ever  been  done. 

Enamelling  (by  which  is  here  meant  the  use  of  a  varnish 
enamel)  has  been  applied  to  water-pipes  for  about  ten  years. 
In  1893-4  a  38-inch  steel-riveted  pipe-line,  about  28  miles  long, 
was  laid  to  supply  the  city  of  Rochester,  N.  Y.,  with  water. 
Half  of  this  pipe,  about  14  miles,  was  protected  by  dipping  the 
sections,  which  were  28  feet  long  and  weighed  up  to  2\  tons,  in 
a  varnish  enamel,  designed  for  the  purpose  by-  the  writer,  and 
were  then  baked.  These  pipes  were  not  pickled;  but  care  was 
taken  that  the  steel  plates  should  not  be  rusted,  and  in  rolling 
such  plates  into  form  they  are  put  under  great  strain  and  all 
the  scale  which  can  be  got  off  is  loosened;  they  were  then  care- 
fully cleaned  before  coating;  the  enamel  was  thin,  probably 
not  over  .003  of  an  inch  in  thickness;  but  the  coated  pipes  stood 


Laying  steel  underfloor  (coated  with  Sabin  Pipe  Coating)  on  Williamsburg 

Bridge,  N.  Y.  City. 

the  subsequent  handling  well,  and  have  now  been  in  service  ten 
years.  Regular  and  frequent  inspection  has  shown  the  coating 
to  be  practically  as  good  as  when  first  applied;  and  in  particu- 

19 


lar  it  has  not  afforded  a  foothold  for  the  growth  of  aquatic  organ- 
isms, a  source  of  much  trouble  in  ordinary  water-mains.  The 
judgment  of  the  engineer,  Mr.  Kuichling,  who  took  the  respon- 


Steel  tmderfloor  (coated  with  Sabin  Pipe  Coating)  ready  to  receive  wood- 
block pavement,  Williamsburg  Bridge,  N.  Y.  City. 

sibility  of  applying  this  coating,  has  thus  been  fully  vindicated. 
The  following  year  the  pipe-line  at  Allegheny,  Pa.,  which  is  nearly 
10  miles  long  and  is  5  feet  in  diameter,  was  similarly  coated; 
these  pipe  sections  were  of  i-inch  plate  and  weighed  5  tons  each; 
the  oven  had  a  capacity  of  8  sections,  or  40  tons,  and  as  much 
as  64  of  these  sections,  or  320  tons,  was  the  output  of  a  single 
day  of  24  hours.  The  same  year  about  4^  miles  of  40-inch  pipe 
was  similarly  treated  for  Cambridge,  Mass.;  all  this  work  has 
been  satisfactory. 

Since  that  time  the  coating  has  been  adopted  for  salt-water 
pipes  (fire-mains  and  flushing-mains)  by  the  U.  S.  Navy  Depart- 
ment, and  is  now  specified  on  all  work  of  this  kind  on  ships  of 
war.  By  its  use  the  durability  of  these  pipes  has  been  increased 
from  fivefold  to  ten  or  twentyfold;  and  plants  for  its  applica- 
tion have  been  erected  in  nearly  all  the  navy  yards  of  this  country. 
Particulars  regarding  the  construction  and  operation  of  these 
plants  will  be  furnished  on  application  by  the  writer. 

20 


In  1902  the  company  with  which  the  author  is  connected  did 
some  novel  and  interesting  work  in  making  a  coating  for  the 
wire  suspension  cables  for  the  Williamsburg  bridge.  In  the  past 
it  has  been  customary  to  protect  such  cables  by  covering  them 
with  white-lead  putty  and  winding  them  with  wire;  this  wire 
is  continuously  wound  from  the  towers  to  the  middle  of  the  cable, 
the  winding  being  as  close  as  possible;  this  protects  the  cable 
from  abrasion  and  makes  a  very  tight  covering.  But  it  is  well 
known  that  putty  gets  hard  and  brittle  after  years  of  age,  and 
may  very  likely  crack  from  vibration  and  changes  of  tempera- 
ture ;  so  it  is  the  practice  to  protect  the  cables  by  frequent  paint- 
ing. It  is  not  practicable  to  cut  through  the  wound-on  coating 
of  wire  to  inspect  the  interior  of  the  cable,  and  the  engineers 
of  the  new  bridge  decided  to  use  a  new  method  of  coating  designed 
in  part  by  us. 

Referring  back  to  what  has  been  said  about  the  drying  of 
linseed-oil,  and  the  use  of  resinous  matters  as  a  flux  to  avoid  its 
gelatinization,  it  may  now  be  added  that  while  it  has  for  hundreds 


Applying  Edward  Smith  &  Co.'s  materials  on  the  saddles  of  the  cables  of 
the  Williamsburg  Bridge. 

of  years  been  known  that  oil  can,  by  blowing  air  through  it,  or 
by  exposing  it  in  films  to  the  air,  be  converted  into  linoxyn,  or 
"  oil-rubber,"  as  it  is  commercially  called,  this  oxidized  oil  (which 

21 


is  commonly  made  by  allowing  the  oil  to  trickle  down  over  sheets 
of  cloth,  forming  a  coating  which  constantly  increases  in  thick- 
ness until  it  is  thick  enough  to  be  mechanically  removed)  is  of 


Applying  Edw.  Smith  &  Co.'s  materials  on  the  cables  of  the  Williamsburg 

Bridge,  N.  Y.  City. 


value  only  for  very  few  and  limited  uses;  it  is  insoluble  in  all 
solvents,  and  is  not  fusible  by  heat;  if  heated  it  chars  but  does 
not  melt;  it  is  therefore  a  very  refractory  material  to  work  with. 
But  many  years  ago.  the  writer  made  a  study  of  the  effects  of 
resinous  fluxes  on  this  material,  especially  to  get  such  a  com- 
pound as  would  retain  as  nearly  as  possible  the  good  qualities — 
elasticity  and  resistance  to  chemical  action — of  the  linoxyn.  Such 
a  compound  was  made,  which  could  be  fused  by  a  moderate 
degree  of  heat,  yet  was  quite  unaffected  by  natural  changes  of 
temperature;  and  in  the  liquid  made  by  melting  this,  cotton 
canvas  was  dipped  and  saturated,  the  excess  of  coating  removed 
as  it  was  drawn  from  the  dip,  and  when  this  coated  canvas  had 
cooled  it  was  perfectly  air  and  water  proof,  yet  was  flexible; 
and  although  it  was  so  free  from  tackiness  that  it  could  be  rolled 
up  on  a  spool,  yet  one  layer  could  be  made  to  adhere  perfectly 
to  another  by  going  over  it  with  a  hot  iron.  This  coated  canvas, 
in  strips  about  10  inches  wide,  was  wrapped  around  the  cable, 
lapping  it  enough  to  make  in  all  three  thicknesses;  and  a  man 
with  a  hot  iron  (such  as  is  used  in  asphalt  paving)  followed  the 

22 


man  who  served  on  the  canvas  and,  as  it  were,  welded  the  whole 
together  into  one  impenetrable  covering. 

This  may  be  cut  open  anywhere  at  any  time  for  examination, 
and  repaired  with  more  of  the  same  material,  as  perfectly  as 
the  original.  The  coated  cable  was  finally  covered  with  a  sec- 
tional tubular  steel  shield,  to  which  the  suspensory  ropes  are 
attached. 

The  compound  in  question  had  been  known  to  the  writer 
for  several  years,  and  its  value  and  permanence  are  beyond  doubt; 
but  the  use  of  canvas  coated  in  this  way  was  new.  It  would 
be  impracticable  to  use  an  ordinary  paint  or  varnish  in  this  way, 
because  these  require  the  accession  of  air  to  oxidize  them,  which 
could  not  be  provided;  the  compound  used,  being  already  oxi- 
dized, is  in  a  perfect  and  mature  state  as  soon  as  it  has  been  applied. 
Canvas  coated  in  this  way  may  be  made  to  adhere  strongly  to 
steel  or  other  metallic  surfaces,  and  no  doubt  will,  if  it  becomes 
known,  find  many  uses  as  a  protective  coating,  as  different  from 
paint  on  the  one  hand  as  it  is  from  cement  on  the  other.  Not 


Applying  Edw.  Smith  &  Co.'s  coating  material  on  cables  of  Williamsburg 

Bridge,  N.  Y.  City. 

only  is  it  ready  for  immediate  exposure  as  soon  as  it  is  put  on, 
but  it  has  the  strength  and  resistance  to  abrasion  of  canvas, 
which  has  long  been  used  to  cover  the  decks  of  yachts,  steam- 

23 


boats,  and  other  vessels,  as  well  as  the  roofs  of  street-cars;  arid 
the  cotton  fibre  is  not  subject  to  decay  if  kept  from  the  weather, 
which  condition  is  .exactly  fulfilled  by  saturating  it  with  this 


Using  a  hot  iron  in  cementing  the  cable  coating  (design  and  material  from 
Edw.  Smith  &  Co.)  on  the  Williamsburg  Bridge,  N.  Y.  City. 

compound.  It  is  not  anticipated  that  such  a  coating  will  take 
the  place  of  paint,  but  may  serve  for  uses  for  which  we  have  as 
yet  had  no  satisfactory  material.  The  introduction  of  a  newT 
kind  of  coating  of  merit  and  of  practical  and  industrial  avail- 
ability is  of  sufficient  importance  to  deserve  more  than  a  pass- 
ing notice.  The  most  serious  defect  of  paint  and  varnish  is  the 
thinness  of  the  film  and  its  consequent  inability  to  resist  abrasion ; 
but  a  heavy  cotton  duck,  weighing  before  coating  three-quarters 
of  a  pound  to  a  square  yard  and  upwards,  is  not  open  to  that 
objection. 

Cleaning  bridgework  preparatory  to  repainting  it  is  a  matter 
of  great  difficulty;  but  it  is  of  the  first  importance,  as  all  engineers 
and  all  paint  manufacturers  agree  that  if  it  is  not  well  done  the 
application  of  paint  is  of  little  use.  The  most  thorough  way 
is  by  the  sand-blast;  this  can  be  accomplished  at  a  cost,  probably, 
of  about  two  cents  per  square  foot.  The  most  important  paper 
on  this  subject  is  one  by  Mr.  Lilly,  of  Columbus,  Ohio,  in  the  Trans- 
actions of  the  American  Society  of  Civil  Engineers,  Volume  50, 
1903;  but  work  in  this  line  is  being  done  in  many  places.  It  is 
attended  by  the  inconvenience  of  dust,  which  may  in  consider- 

24 


able  part,  but  not  wholly,  be  obviated  by  screens  of  cloth.  In 
isolated  places  this  is  of  little  account.  If  for  any  reason  this 
is  not  thought  practicable,  it  is  necessary  to  thoroughly  scrape 
and  then  wire-brush  the  surface.  Some  bridge  gangs  are  equipped 
with  complete  sets  of  scrapers,  some  of  which  are  wide,  some 
narrow;  most  are  straight,  but  some  are  hooked  like  a  hoe,  to 
be  operated  by  pulling  instead  of  pushing;  they  should  all  be 
long  enough  to  be  firmly  grasped  by  both  hands,  and  a  hammer 
and  chisel  are  sometimes  useful  auxiliaries.  In  1903  the  Chicago  & 
Northwestern  Railroad  cleaned  their  train -shed  in  Chicago  by 
scraping,  after  which  a  considerable  part  of  the  surface  was  washed 
with  acid,  which  was  subsequently  removed  by  alkali;  then 
washed,  dried,  and  brushed  before  painting.  In  one  of  the  largest 
chemical  works  in  the  country  iron  is  pickled  with  rather  strong 
sulphuric  acid  (the  stronger  it  is,  up  to  say  30  per  cent,  the  more 
rapidly  it  acts),  then  this  is  immediately  neutralized  with  hot 
milk  of  lime,  no  intermediate  washing  being  done;  the  milk  of 
lime,  made  by  slaking  lime  in  water,  is  cheap  material,  and  may 


Applying  Edw.  Smith  &  Co.'s  coating  material  on  cables  of  Williamsburg 

Bridge,  N.  Y.  City. 

be  either  rinsed  off  with  water  or  allowed  to  dry  on  and  then 
removed  with  a  brush.  This  is  excellent  practice.  Iron  treated 
in  this  way  is  not  so  extremely  prone  to  rust  as  is  sand-blasted 

25 


metal,  but  of  course  should  be  painted  with  the  very  least 
possible  delay.  The  wire  brush  is  certainly  a  most  useful  and 
efficient  implement  for  getting  dirt  off  metal;  but  it  should  not 
be  depended  on  for  the  removal  of  scale  or  thick  and  strongly 
adherent  rust.  In  our  own  factory  we  have  a  large  rotary  wire 
brush  driven  by  power,  which  is  naturally  more  efficient  than  a 
hand-brush ;  but  even  this  will  not  remove  anything  which  adheres 
very  persistently.  Thorough  scraping  should  precede  brushing. 
If  it  is  certain  that  the  old  paint  which  was  on  the  bridge  was 
of  good  quality,  which  can  be  easily  told  at  the  time  of  repaint- 
ing, and  if  it  is  in  part  in  good  condition,  as  is  sometimes  the 
case,  it  is  not  absolutely  necessary  to  remove  it;  and  in  fact  I 
think  bridges  should  not  be  left  without  painting  repairs  until 
the  old  paint  is  destroyed.  A  better  way  is  to  keep  watch  of  the 
structure  and  when  any  considerable  break  appears  in  the  paint 
let  that  place  be  cleaned  and  repainted.  An  engineer  would 
not  wait  until  all  the  bolts  and  rivets  rusted  out  of  a  bridge  before 
he  began  to  put  new  ones  in,  and  I  see  no  reason  why  all  repairs 
should  not  be  made  in  the  same  manner, 

26 


Williamsburg  Bridge,  N.  Y.  City.  Cables,  floor,  and  anchorage  metal  work 
protected  with  Edward]  Smith  &  Co.'s  coatings.  L.  L.  Buck,  Ch.  Eng. 
O.  F.  Nichols,  Prin.  Asst.  Eng. 


Charlestown  Bridge,  Boston.     Wm.  Jackson,  City  Engr.      The  girders  were 
painted  with  Durable  Metal  Coating,  the  rest  of  the  bridge  with  Pelagic]  3 
Enamel,  made  by  Edward  Smith  &  Co.,  N.  Y. 

28 


II. 

SPECIFICATIONS  FOR  BEST  WORK. 

I.  All  iron  or  steel,  after  being  shaped,  punched,  bored,  and 
otherwise  made  ready  for  assembling,  must  be  cleaned  by  the 
sand-blast  or  other  equally  efficient  means,  so  as  to  show,  in  all 
parts,  the  grayish-white  color  of  the  metal. 

The  cleaning  of  structural  steel  work  by  the  use  of  the  sand- 
blast is  probably  the  simplest  and  most  satisfactory  way  to  have 
it  done.  The  great  objection  to  this,  as  to  all  such  work,  is  the 
cost.  Since  there  are  practically  no  plants  for  doing  such  work 
in  bridge ,  shops — in  fact  there  are  no  plants  for  cleaning  steel 
by  any  process — any  engineer  who  decides  to  call  for  thorough 
cleaning  must  expect  to  pay  an  additional  sum  for  such  work, 
which,  if  the  work  be  of  small  extent,  will  be  disproportionately 
great  in  comparison  with  the  work  actually  done;  but  if  the 
work  be  of  great  extent  the  incidental  cost  of  the  plant  will  make 
but  a  small  item  in  the  total  cost.  Plants  have  been  installed 
since  the  publication  of  the  first  edition  of  these  specifications  by 
several  of  the  railroad  companies  for  cleaning  bridges  in  place, 
by  some  municipal  engineers,  and  by  some  manufacturing  works 
where  structural  metal  is  treated.  It  has  been  objected  that  this 
is  a  patented  process;  it  is  therefore  in  order  to  observe  that 
the  original  patent,  under  which  work  of  great  extent  was  carried 
on  most  successfully  for  fifteen  years;  was  issued  to  Gen.  Benj.  G. 
Tilghman,  of  Philadelphia,  on  Oct.  18,  1870,  being  No.  108,408, 
and  has  therefore  expired  long  ago. 

Among  the  most  important  claims  granted  by  that  patent 
were  the  following: 

"  i.  The  cutting,  boring,  dressing,  engraving,  and  pulver- 
izing of  stone,  metal,  glass,  pottery,  wood,  and  other  hard  or 
solid  substances  by  sand  used  as  a  projectile  when  the  requisite 
velocity  has  been  imparted  to  it  by  any  suitable  means. 

"2.  The  artificial  combination  of  a  jet  or  current  of  steam, 

29 


air,  water,  or  other  suitable  gaseous  or  liquid  medium  with  a 
stream  of  sand,  as  a  means  of  giving  velocity  to  the  sand  when 
the  same  is  used  as  a  projectile  as  a  means  of  cutting,  boring, 
dressing,"  etc.,  etc. 

"7.  When  a  jet  or  current  of  steam,  air,  water,  or  any  other 
suitable  gaseous  or  liquid  medium  is  employed  to  give  velocity 
to  sand  used  as  a  projectile,  as  a  means  of  cutting,  boring,  dress- 
ing," etc.;  "  the  use  of  the  following  devices  for  introducing  the 
sand  into  the  jet  of  steam,  air,  water,  etc.:  First,  the  suction 
produced  by  the  jet  of  steam,  air,  water,  etc.  Second,  a  strong, 
close  vessel,  or  sand-box,  into  which  the  pressure  of  the  steam, 
air,  water,  etc.,  is  introduced,  and  through  which,  when  desired, 
a  current  of  it  may  be  made  to  pass." 

It  is  obvious  from  the  foregoing  that  there  is  no  existing  patent 
on  the  process ;  and  while  there  is  some  patented  apparatus  which 
is  preferred  by  some  of  the  people  who  use  the  process,  this  is 
equally  true  of  a  very  large  proportion  of  all  machinery  in  use. 
The  process  of  cleaning  with  the  sand-blast  is  essentially  as  follows : 
Air  at  a  pressure  of  20  to  25  pounds  per  square  inch  is  furnished 
by  any  suitable  air  compressor.  If  we  assume  that  we  will  use 
a  discharging  nozzle  9-16  inch  internal  diameter  when  new, 
each  such  nozzle  will  require  120  cubic  feet  of  air  per  minute, 
measured  at  atmospheric  pressure  compressed  to  show  a  pressure 
of  15  pounds  per  square  inch  at  the  nozzle.  This  is,  how- 
ever, to  be  regarded  as  a  minimum,  for  it  is  advisable  to 
use  a  somewhat  higher  pressure,  say  20  pounds;  and  tKe 
nozzle  rapidly  wears  away  until  it  reaches  a  diameter  of  J 
inch,  at  which  it  will  discharge  nearly  twice  as  much  as  when 
new,  so  that  in  practice  it  is  well  to  provide  an  air-compressor 
handling  240  cubic  feet  of  air  per  minute  and  compressing  the 
same  to  20  pounds  per  square  inch.  For  four  of  these  nozzles, 
each  connected  with  a  No.  6  Ward  &  Nash  apparatus,  an  Inger- 
soll  compressor  of  24-inch  stroke,  2 2 -inch  steam,  and  22-J-inch 
air-cylinder  was  used;  and  such  a  plant  ought  to  be  supplied 
with  steam  from  a  150-!!. P.  boiler.  These  latter  figures  are,  of 
course,  rough;  but  from  the  number  of  cubic  feet  of  air  used 
and  the  pressure  any  one  can  compute  the  rest  of  the  plant.  It 
has  been  found  that  for  the  removal  of  hard,  tough  scale,  a  pres- 
sure of  35  pounds  per  square  inch  is  necessary. 

Into  this  current  of  air  dry  sand  is  introduced  at  the  rate  of 
about  10  cubic  feet  of  sand  per  hour  for  each  such  nozzle,  or 
i  cubic  foot  of  sand  to  1000  cubic  feet  of  air.  The  sand  must 
be  artificially  dried.  Some  operators  use  coarsely  powdered  quartz ; 

30 


this  latter  can  be  used  five  times  in  succession;  and  in  general 
the  sand  may  be  used  until  it  is  broken  up  into  a  powder  too 
fine  for  use.  In  the  plants  which  the  writer  has  inspected  the 
sand  and  air  are  carried  to  the  nozzle  through  a  heavy  rubber 
hose  about  2^  inches  in  diameter.  This  is  not  worn  away  by  the 
current  as  a  metal,  pipe  would  be;  but  it  is  necessary  that  the 
air  should  not  be  hot,  as  this  would  rapidly  injure  the  hose.  The 
nozzles  are  short  pieces  of  chilled-iron  pipe,  and  have  to  be 
renewed  at  frequent  intervals.  From  data  furnished  me  by 
Naval  Constructor  Bowles  I  find  that  the  cost  of  cleaning  the 
bottom  of  a  ship  in  dry  dock  amounted  to  about  4  cents  per  square 
foot;  but  this  was  done  with  an  experimental  plant,  and  the 
method  of  drying  the  sand,  which  was  used  only  once,  was  costly, 
and  the  cost  would  certainly  have  been  reduced  to  3  cents  per 
square  foot  if  a  permanent  plant  had  been  in  use.  Since  the  instal- 
lation of  a  permanent  plant  no  work  has  been  done  of  sufficient 
magnitude  to  give  figures.  This  was  an  exceedingly  rusty  sur- 
face; but  with  this  same  experimental  plant  the  mill  scale  was 
removed  from  3,55  square  feet  of  surface  of  steel  plates  at  a 
cost  of  $17.60,  or  about  \  cent  per  square  foot,  and  at  the  rate 
of  4}  square  feet  per  minute  per  nozzle. 

Work  recently  done  indicates  that  bridgework  may  be  cleaned 
in  the  field  by  this  process  for  2  cents  per  square  foot. 

It  may  be  well  to  add  that  in  all  the  work  referred  to,  which 
was  practically  field^  work,  being"]  carried  on  out-of-doors  and 
with  a  somewhat  portable  plant,  the  labor  amounted  to  one 
man  to  hold  each  nozzle,  one  man  to  attend  to  each  two  sand- 
Doxes,  and  one  man  to  clean  up  and  carry  sand  for  each  four 
nozzles.  The  supply  of  compressed  air  is  an  expense  of  a  differ- 
ent sort,  as  is  also  in  field  work  the  matter  of  staging,  etc.;  but 
all  are  included  in  the  prices  given.  It  seems  reasonable  to  sup- 
pose that  where  many  pieces  of  metal  of  the  same  general  char- 
acter are  to  be  treated  in  a  shop  fitted  up  for  the  purpose,  con- 
trivances may  be  introduced  which  will  do  away  with  a  con- 
siderable part  of  the  labor. 

Iron  and  steel  may  also  be  cleaned  by  picklinsr  in  acid  and  the 
subsequent  removal  of  the  latter.  This  may  be  done  in  the  fol- 
lowing manner :  The  pieces  of  metal  which  have  been  made  ready 
for  assembling  are  immersed  in  hot  dilute  sulphuric  acid  having 
a  strength  of  25  to  28  per  cent.  Some  use  acid  of  20  per  cent. 
It  is  kept  in  this  until  the  whole  surface  is  free  from  rust  and 
scale;  this  will  take  from  6  to  12  minutes.  If  the  pieces  of  metal 
are  somewhat  rusty,  so  that  rust  has'  started  underneath  the 

31 


The    steel    framework   of   the    Broadway   Chambers    Building,    N.  Y.,  was 

painted  with  Ebonite  Varnish. 

32 


scale,  the  shorter  time  will  be  found  sufficient;  but  if  it  con- 
sists of  plates  covered  with  closely  adherent  blue  or  iridescent 
rolled  scale,  the  longer  time  will  be  necessary,  since  this  scale 
is  itself  insoluble  in  acid  and  is  removed  by  the  latter  penetrat- 
ing the  innumerable  minute  cracks  in  the  scale  and  attacking 
the  iron  underneath,  thus  mechanically  throwing  off  the  scale. 
If,  on  the  other  hand,  the  iron  is  uniformly  rusty,  this  coating 
of  hydrated  oxide  readily  dissolves  in  acid;  and  in  fact  a  weaker 
acid  of  10  per  cent  to  12  per  cent  might  be  used,  although  the 
stronger  acid  is  quite  safe,  but  will  require  a  shorter  time.  It 
has  been  suggested  that  it  is  desirable  to  previously  clean  the 
metal  with  caustic  alkali  from  all  grease,  etc.;  but  if  acid  of  the 
above  strength  is  used^and  kept  as  hot  as  possible  this  will  not 
be  necessary.  As  soon  as  the  acid  has  reached  the  iron  in  all 
parts  of  the  surface  the  metal  is  taken  out  and  washed  by  jets 
of  water  discharged  against  it  under  high  pressure,  not  less  than 
100  pounds  per  square  inch,  and  much  better  if  double  that. 
In  this  way  the  acid  may  be  thoroughly  removed. 

In  Germany  it  is  said  to  be  customary  to  use  acid  of  9  or  10 
per  cent  cold,  and  the  metal  is  left  in  it  five  hours.  This  makes 
a  much  larger  plant  necessary  and  has  no  advantages. 

If  it  is  attempted  to  remove  the  acid  by  soaking  the  metal 
in  still  water  the  following  difficulty  is  encountered:  the  iron 
becomes  immediately  coated  with  a  gummy  or  colloidal  substance 
very  difficult  to  remove.  What  this  is,  is  not  known  to  the  writer; 
but  it  is  well  knownjthat  there  are  a  number  of  insoluble  or  diffi- 
cultly soluble  compounds  of  iron  with  sulphuric  acid,  and  it  is 
probable  that  some  of  these  are  precipitated  on  the  surface  of 
the  iron  when  water  removes  the  excess  of  acid;  but  if  a  jet  of 
water  is  used  the  mechanical  effect  .is  to  remove  the  adherent 
ferrous  sulphate  at  the  same  instant,  leaving  a  clean  metallic 
surface.  It  is  also  possible  that  if  the  acid  contains  arsenic , 
as  is  the  case  with  much  of  the  acid  made  from  pyrites,  this  may 
also  be  precipitated  on  the  surface;  in  fact  it  is  sure  to  be,  and 
acid  free  from  arsenic  should  always  be  used  for  this  purpose, 
and  as  a  matter  of  practice  it  is  insisted  on  by  many. 

Very  successful  work  is  now  done  by  (i)  dipping  the  metal 
in  10  per  cent  solution  of  caustic  soda,  boiling  hot;  (2)  in  boiling 
water;  (3)  in  hot  10  per  cent,  sulphuric  acid;  (4)  in  boiling 
water;  (5)  in  hot  10  per  cent  carbonate  of  soda;  (6)  in  boiling 
water;  then  put  in  the  oven  to  dry.  The  process  is  economical 
and  the  results  are  all  that  could  be  desired. 

It  is  often  difficult  and  sometimes  impracticable  to  pickle 

33 


steel  high  in  carbon,  and  cast  iron  containing  graphitic  carbon, 
on  account  of  the  deposit  of  a  film  of  carbon,  like  stove-blacking, 
on  the  surface.  Muriatic  (chlorhydric)  acid  has  been  used  instead 


One  of  a  group  of  four  bridges  on  the  Boston  &  Albany  R.R.,    all  painted 
with  Durable  Metal  Coating.     W.  Shepard,  Ch.  Eng. 

of  sulphuric;  but  it  is  not  well  suited  for  the  purpose,  being  much 
more  expensive  and  difficult  to  remove.  It  also  forms  a  gummy 
coating  on  the  iron,  worse  than  that  with  sulphuric;  and  in  the 
subsequent  alkaline  treatment  it  must  be  removed  by  caustic 
soda  instead  of  lime,  or,  better,  by  a  solution  of  sulphate  of  zinc. 

After  the  iron  has  been  freed  from  sulphuric  acid  in  the  man- 
ner just  described,  it  is  put  in  a  bath  of  lime-water  or  milk  of 
lime,  boiling-hot  (it  is  very  important  that  it  should  be  hot), 
and  left  there  long  enough  to  reach  the  temperature  of  the  liquid. 
It  is  then  removed  to  an  oven  and  dried,  after  which  the  lime  is 
brushed  off.  If  desired  the  lime  may  be  removed  by  washing 
before  putting  in  the  oven ;  in  this  case  it  will  be  found  that  the 
surface,  which  is  perfectly  clean  and  bright,  rusts  very  easily 
and  quickly;  whereas  if  the  lime  is  removed  by  drying  and  brush- 
ing, the  surface  is  much  less  likely  to  rust,  although  even  then 
it  rusts  easily  and  should  be  painted  immediately. 

For  most  of  the  foregoing  information  relating  to  pickling 
I  am  indebted  to  Mr.  E.  G.  Spilsbury,  who  has  had  extensive 
experience  in  this  work  both  in  Europe  and  the  United  States, 
and  has  applied  the  process  to  structural  steel  (bridge)  work,  as 
well  as  to  wire  and  wire  rods.  Mr.  Spilsbury  estimates  the  total 
expense  of  pickling  and  cleaning  steel  for  bridgework  in  a  modern 
and  well-arranged  plant  at  about  25  cents  per  ton.  As  to  the 
time  when  the  cleaning  is  to  be  done,  it  may  be  said  that  the 

34 


metal  may  be  cleaned  before  it  reaches  the  shop  at  all.  This 
is  in  one  respect  a  simpler  method,  as  requiring  less  handling. 
It  is  obviously  impracticable  to  do  the  work  of  cleaning  either 
by  the  sand-blast  or  acid  in  the  shop  itself,  and  the  method  speci- 
fied involves  the  removal  of  the  pieces  from  the  shop  and  bring- 
ing them  back.  This  extra  labor  is  variously  estimated  by  shop 
owners  and  managers  who  have  been  consulted  at  from  50  cents 
to  $2  per  ton;  doubtless  some  have  much  better  facilities  than 
others;  and  there  will  also  be  a  difference  of  cost  in  handling 
light  or  heavy  work.  To  offset  this  extra  charge,  which  would 
be,  if  we  average  the  estimates  of  the  persons  consulted,  about 
$i  per  ton,  we  save  the  application  of  a  shop  coat  of  oil.  The 
metal  will  remain  in  the  shop  not  less  than  a  week,  as  an  aver- 
age; and  it  is  necessary  that  it  should  be  protected  during  that 
time  from  rust.  The  shop  men  all  agree  that  it  will  not  do  to 
paint  it  at  that  time,  and  that  an  oil  coat  is  the  only  thing  which 
is  practicable.  It  is  quite  well  known  that  raw  linseed-oil  is 
much  more  durable  than  boiled  oil,  and  if  we  apply  a  coat  of 
boiled  oil,  which  will  dry  in  about  twenty-four  hours,  we  are 
in  the  irrational  position  of  having  taken  great  care  to  secure  a 
perfect  surface  and  then  applied  a  foundation  coat  of  inferior 
material. 

So  we  are  brought  to  the  necessity  of  using  raw  oil;  and  this 
will  require  about  a  week  to  dry,  during  which  time  the  metal 
certainly  ought  to  be  kept  under  cover.  The  expense  of  this 


Erie  R.R.  bridge  at  Salisbury  Mills,  N.  Y.      Painted  with   Durable  Metal 

Coating. 

coat  of  oil,  applied  in  this  manner,  is  variously  estimated  at  from 
50  cents  to  $i  per  ton;  and  it  is  pretty  generally  agreed  that 
the  result  of  this  method  of  doing  the  work  will  not  be  as  good 

35 


as  the  specified  method.  For  it  must  be  remembered  that  dry 
linseed-oil  is  not  a  hard  substance  like  a  varnish  film,  but  is  a 
gummy  substance,  which  during  the  shop  handling  will  get  dirty 
with  solid  matter  and  with  machine-oil,  which  cannot  be  removed 
and  must  subsequently  be  painted  over;  while,  if  we  wait  until 
the  shop  work  is  done,  all  but  the  assembling,  we  get  the  sur- 
faces perfectly  clean,  and  can  then  apply  our  shop  coat  of  paint, 
which  will  be  dry  so  it  may  be  handled  in  forty-eight  hours;  and 
then  when  we  rivet  it  up  we  can  apply  a  second  coat  of  fresh 
paint  to  the  surfaces  to  be  riveted  together,  which  are  by  far 
the  most  important  to  preserve,  as  it  is  in  these  and  other  crevices 
that  most  of  the  dangerous  rusting  is  likely  to  occur,  especially 
if  the  work  is  properly  cared  for  in  the  way  of  maintenance. 
More  will  hereafter  be  said  in  regard  to  the  matter  of  shop  coat 
of  oil. 

II.  Immediately  after  being  so  cleaned,  and  before  any  dis- 
coloration due  to  rusting  has  begun,  the  material  shall  be  care- 
fully inspected,  and  upon  the  approval  of  the  inspector,  shall  receive 
one  full  coat  of  Durable  Metal  Coating  made  by  Edward  Smith  &  Co., 
of  45  Broadway,  New  York  City ;  except  planed  and  turned  surfaces, 
which  shall  be  coated  with  Vacuum  Flushing  Oil  and  shall  be 
kept  so  coated  until  they  are  erected  in  place. 

In  order  to  carry  this  section  into  effect  it  will  be  necessary 
to  paint  the  work  at  once,  within  one  or  two  hours  of  the  time 
when  it  is  cleaned.  If  the  metal  has  been  pickled  it  will  there- 
fore be  hot  from  the  oven;  it  is  then  in  the  best  condition,  for 
paint  spreads  better  and  penetrates  crevices  when  the  metal 
is  hot,  and  there  is  practically  no  air  film  on  the  metal  to  be  dis- 
placed. It  is  the  opinion  of  many  engineers  that  the  best  results 
would  be  obtained  by  immersing  the  pieces  of  iron  or  steel  in  a 
tank  of  hot  paint,  at  a  temperature  of  about  175°  F.,  and  leaving 
it  there  fifteen  minutes  or  more.  By  doing  so  all  the  surface 
would  be  reached,  and  it  is  probable  that  such  a  course  would 
show  great  economy  of  labor,  which  is  the  most  important  item 
of  cost  in  painting.  It  must  be  remembered,  whatever  method 
is  adopted,  that  the  most  important  matter  about  this  whole 
work  is  to  get  the  best  possible  foundation  coat  attached  as  securely 
as  possible  to  the  metal;  the  subsequent  cost  of  maintenance 
will  be  greatly  reduced  if  this  is  effectively  done. 

This  is  the  crucial  point  of  the  whole  work  of  painting. 

36 


III.  The  metal  shall  not  be  exposed  to  the  weather  nor  taken 
to  the  shop  until  in  the  opinion  of  the  inspector  the  paint  is  suffi- 
ciently dry.     At  no  time  after  the  preliminary  cleaning  shall  the 
pieces  of  iron  or  steel  be  laid  on  the  ground,  but  shall  be  laid  on 
skids  or  trestles,  and  in  all  handling  and  loading  and  unloading 
of  the  same  care  shall  be  taken  to  avoid  scraping  off  the  preserva- 
tive coating;    and  in  transportation  care  shall  be  taken  to  avoid 
nesting  the  pieces  except  with  packing  material  between  them. 

It  is  not  expected  that  the  work  will  be  held  in  the  paint  shop 
until  the  paint  is  thoroughly  dry,  but  only  until  it  has  got  its 
initial  set  throughout;  but  of  this  the  inspector  is  to  be  the  judge. 
It  is  probable  that  it  will  take  two  days,  sometimes  three. 

IV.  After  being  taken  back  to  the  shop  all  surfaces  which  are 
to  be  there  riveted  or  bolted  together  are  to  be  cleaned,  if  necessary, 
and  painted  on  each  such  surface  with  a  second  coat  of  said  Dur- 
able Metal  Coating;    only  such  parts  of  surfaces  as  are  to  be  thus 
brought  in  contact  are  to  be  so  treated.     After  riveting,  all  small 
cavities  which  will  hereafter  be  inaccessible  shall  be  rilled  with  a 
mixture  of  one  part  Portland  cement  and  three  parts  clean  sand, 
with  a  proper  amount  of  water. 

V.  After  erection  the  work  shall  be  carefully  inspected,  and  if 
there  are  any  rusty  spots  these  shall  be  thoroughly  cleaned  and  all 
such  places  and  also  places  where  the  paint  has  been  rubbed  off  shall 
receive  a  coat  of  Edward  Smith  &  Co.'s  Durable  Metal  Coating;  and 
all  exposed  edges  and  angles  shall  receive  an  extra  striping  coat  of 
the  same,  covering  the  edge  and  the  adjacent  surface  one  or  two 
inches  from  the  edge  on  each  side ;  all  rivet-  and  bolt-heads  and  nuts 
shall  also  receive  an  extra  coat ;  after  this  has  become  dry  the  whole 
surface,  having  previously  been  thoroughly  cleaned  from  dirt,  shall 
receive  another  full  coat  of^said  Durable  Metal  Coating. 

When  paint  begins  to  dry  there  is  at  first  a  sort  of  skin  formed 
on  the  surface,  which  contracts,  and  on  rounded  surfaces  like 
rivet-heads,  and  on  angles  and  edges,  seems  to  press  away  the 
liquid  paint  beneath,  so  that  on  such  surfaces  there  is  less  than 
the  normal  amount.  The  same  tendency  to  contract  also  exists 
on  flat  surfaces,  but  in  this  case  it  is  a  balanced  tension  and  pro- 
duces no  effect.  There  is  besides  the  action  of  the  painter's 
brush,  which  presses  harder  on  such  places  and  draws  off  the 
paint;  but  that  this  is  not  the  main  cause  is  shown  by  the  fact 
that  pipe  sections  and  other  things  which  have  been  coated  by 
dipping  exhibit  the  same  appearance.  In  making  paint  tests, 

37 


it  is  necessary  to  leave  out  of  account  a  strip  about  an  inch  wide 
along  the  edges  of  the  plate,  unless  that  portion  has  received 
an  extra  coat;  and  the  fact  is  well  known  to  inspectors  that  such 


Drawbridge  at  Ashtabula  Harbor,  L.  S.  &  M.  S.  R.R.    E.  A.  Handy,  Ch.  Eng. 
Painted  with  Durable  Metal  Coating. 

surfaces  are  always  thinly  coated.  The  extra  striping  coat  is 
therefore  necessary  if  we  are  to  have  two  full  coats  or  their  equiva- 
lent over  the  whole  surface ;  and  it  is  the  more  important  because 
these  portions  are  more  exposed  than  the  flat  surfaces. 

VI.  In  no  case  shall  a  second  or  third  coat  of  paint  be  applied 
until  the  previous  one  is  entirely  dry. 

VII.  During  erection  any  small  cavities  which  will  hereafter 
be  inaccessible  shall  be  filled  as  provided  in  Section  IV. 

VIII.  After  receiving  the  second  coat  of  Durable  Metal  Coating, 
and  after  the  same  has  become  quite  dry,  the  whole  structure  shall 
receive  two  coats  of  such  paint  as  may  be  designated  and  approved 
by  the  engineer,  the  pigment  in  such  paint  to  consist  of  two  parts 
by  weight  of  white  lead  and  one  part  of  white  zinc,  tinted  to  a 
designated  shade;    and  the  vehicle  to  be  a  varnish  composed  of 
only  hard  varnish  resins  and  pure  linseed-oil  and  turpentine,  the 
oil  being  in  the  proportion  of  not  less  than  two  parts  by  weight 
of  oil  to  one  part  by  weight  of  the  aforesaid  resin  weighed  before 
melting;    and  the  product  to  be  free  from  common  rosin,  benzine, 
and   mineral-oil   products;    and  samples  of  the  paint  which  the 
contractor  proposes  to  use  for  this  work  shall  be  obtained  not  less 
than  one  hundred  days  in  advance  and  submitted  to  the  engineer 
for  examination  and  approval,  and  no  such  paint  shall  be  used 
unless  approved  by  him,  and  his  rejection  of  any  paint  shall  be 
final;    and  when  such  sample  has  been  approved,  the  contractor 


must  use  the  paint  made  by  the  same  manufacturer  who  made 
the  sample,  and  the  paint  must  be,  when  used,  exactly  the  same 
in  every  respect  as  the  tested  sample  and  must  not  be  thinned  down 
or  adulterated  or  changed  in  any  way  whatever;  and  it  shall  be 
used  subject  to  all  the  conditions  mentioned  in  the  following  section. 

Section  VIII  is  intended  exclusively  for  structures  which 
must  be  painted  a  light  color.  The  only  pigments  which  can 
be  used  as  a  base  for  light-colored  paints  are  white  lead  and  white 
zinc;  neither  of  these  is  regarded  as  very  durable,  but  their  use 
is  absolutely  unavoidable.  A  mixture  of  the  two  is  regarded 
as  better  in  many  ways  than  either  alone.  They  may  be  mixed 
with  good  results  in  any  proportion  from  two  parts  of  lead  to 
one  of  zinc,  to  one  part  of  lead  to  two  of  zinc;  the  former  pro- 
portion is  a  very  common  one.  They  are  liable  to  be  adulterated 
with  sulphate  of  baryta,  carbonate  of  lime  (whiting),  china-clay 
and  ground  feldspar.  None  of  these  has  any  value,  and  paint 
containing  any  of  them  should  be  rejected.  White-lead  paint 
has  a  tendency  to  show  a  granular  surface  which  will  brush  off; 
it  "  chalks,"  to  use  the  painter's  words;  zinc  tends  to  come  off 
in  flakes.  On  this  account  it  is  better  to  use  a  varnish  as  a 
vehicle  or  binder  rather  than  oil,  as  the  former  has  more  hardness 


Forty-inch  riveted  steel  pipe,  Cambridge,  Mass.,  1895.      Coated  with  Sabin 

Pipe  Coating. 

and  tenacity;  moreover,  a  varnish  paint,  if  made  of  good  mate- 
rials, is  more  impenetrable  to  air  and  water,  and  therefore  more 
desirable.  But  it  is  important  that  the  varnish  should  be  suited 

39 


to  the  purposes.  As  a  rule,  the  larger  the  proportion  of  oil  to 
resin  the  more  elastic  and  durable  is  the  varnish;  but  a  point  is 
reached  when  the  resin  appears  to  be  saturated  with  oil,  bevond 


Sixty-inch   riveted   steel   pipe,   Allegheny,    Pa.,    1895. 

Pipe  Coating. 


Coated   with   Sabin 


which  any  more  oil  has  a  deleterious  effect.  The  exact  pro- 
portions vary  with  the  kind  of  resin,  and  also  depend  on  some 
other  conditions;  but  in  general  the  most  durable  varnishes  con- 
tain from  two  to  two  and  a  half  times  as  much  oil  as  resin,  the 
latter  being  weighed  before  melting,  during  which  process  it 
loses  about  one-fourth  its  weight.  Such  a  paint  will  not  be 
required  to  be  perfectly  white,  being  usually  tinted  to  some  desig- 
nated color,  and  can  be  sold  in  large  quantities  at  a  price  prob- 
ably not  more  than  30  or  40  per  cent  more  than  a  straight  lead- 
and-oil  paint  will  cost;  it  will  be  found  much  more  economical. 
As  to  testing  such  a  paint,  it  is  absolutely  necessary  to  have  a 
reasonable  time,  and  100  days  is  little  enough.  It  would  be  better 
to  have  more.  Of  course,  if  it  is  admissible  to  leave  the  struc- 
ture black  this  section  will  be  omitted;  but  in  that  case,  for  really 
high-class  work  such  as  these  specifications  contemplate,  a  third 
coat  of  the  protective  coating  will  be  advisable.  It  is  expected 
that  the  coating  of  white  or  light-colored  paint  will  require  to  be 
renewed  from  time  to  time,  while  the  durable  metal  coating  is 
depended  on  for  permanent  protection. 

40 


IX.  All  paint  and  Durable  Metal  Coating  used  for  this  work 
shall  be  purchased  directly  from  the  manufacturer  or  his  authorized 
agent,  and  each  shipment  shall  be  accompanied  by  a  signed  cer- 
tificate from  the  manufacturer  or  such  agent,  stating  that  he  has, 
at  that  time,  shipped  a  specified  amount  of  the  specified  paint  or 
Durable  Metal  Coating;  and  all  paint  and  Durable  Metal  Coating 
shall  be  brought  on  to  the  premises  where  they  are  to  be  used  in 
the  manufacturers'  sealed  packages,  which  shall  be  opened  in  the 
presence  of  the  inspector,  who  may  then,  and  at  any  subsequent 
time,  take  samples  for  examination  or  analysis;  and  in  case  any 
analysis  made  by  direction  of  the  chief  engineer  shows  impurity, 
adulteration,  or  substitution  in  these  specified  materials,  the  con- 
tractor shall  pay  all  the  costs  of  such  analysis,  and  shall  more- 
over thoroughly  clean  off  all  metal  coated  with  such  impure  or 
unauthorized  material  and  shall  repaint  it  to  the  satisfaction  of  the 
inspector.  And  the  contractor  shall,  upon  demand,  exhibit  to  the 
engineer  or  inspector  the  bills  from  the  manufacturers  or  their 
agents,  showing  the  amount  of  paint  and  Durable  Metal  Coating 
purchased,  and  also  the  certificates  spoken  of  in  this  section;  and 
neither  the  paint  nor  the  Durable  Metal  Coating  shall  be  thinned 


Sixty-inch   riveted   steel   pipe,   Allegheny,    Pa.,    1895.     Coated   with   Sabin 

Pipe  Coating. 

with  anything  whatsoever,  nor  shall  any  turpentine  or  benzine  be 
allowed  upon  the  premises  for  any  purpose,  except  by  permission 
of  the  inspector  and  in  such  quantity  as  he  may  allow. 


X.  The  inspector  shall  be  notified  when  any  painting,  either 
with  Durable  Metal  Coating  or  other  material,  is  to  be  done,  and 
no  such  work  is  to  be  done  until  the  inspector  has  approved  the 
surface  to  which  it  is  to  be  applied;    and  the  contractor  shall  fur- 
nish  all   facilities   for  inspection   and   for   necessary  marking   by 
the  inspector,  and  all  materials,  such  as  paint,  brushes,  etc.,  for 
such   marking.     No    such   inspection    or   marking   shall   be    done 
except  by  the  engineer  or  his  authorized  inspector. 

XI.  In  no  case  shall  any  paint  be  applied  out-of-doors  in  freezing, 
rainy,  or  misty  weather,  and  all  surfaces  to  which  paint  is  applied 
must  be  at  the  time  dry  and  clean;    and  all  work  must  te  done  in 
a  thorough,  neat,  and  workmanlike  manner.     If  it  is  necessary,  in 
cool  weather,  to  thin  the  paint,  this  may  be  done  only  by  heating 
it;    and  this  may  be  required  by  the  inspector. 

The  practice  of  heating  paint  before  it  is  applied  has  been 
followed  for  a  considerable  time  by  some  of  the  best  engineers. 
It  is  sometimes  done  by  keeping  several  tin  pails  of  paint  in  a 
hot-water  tank,  kept  hot  by  exhaust  steam;  or  where  there  is 
no  steam  plant  it  is  heated  directly  over  a  small  oil-stove  or  other 
source  of  heat.  If  heated  from  125°  to  150°,  which  is  perfectly 
safe  if  the  paint  contains  no  benzine — in  fact  it  may  safely  be 
heated  as  hot  as  boiling  water  will  make  it — it  flows  much  more 
freely,  and  penetrates  the  crevices  of  the  work  much  better.  It  is 
indeed  likely  to  make  a  thin  coat,  which  is  objectionable;  but 
the  advantages  outweigh  the  disadvantages. 

XII.  The  foregoing  specifications  shall  be  accepted  and  carried 
out  faithfully  in  every  particular  and  shall  not  be  construed  accord- 
ing to  any  prevalent  practice  not  in  full  accord  therewith. 

4? 


1 1  ift 


Fayerwether  Hall,  Yale  University.      Edward  Srrith  &  Co.'s  coatings  used 
throughout  on  this  building. 

44 


III. 

SPECIFICATIONS  FOR  ORDINARY  WORK. 

I.  Shortly  before   riveting,   all   such  parts   of  surfaces   as   are 
to  be  brought  permanently  into  contact  shall  be  thoroughly  cleaned 
from  dirt  and  rust,  and  from  all  scale  which  does  not  perfectly 
adhere  to  the  metal,  by  the  use  of  scrapers,  chisels,  and  wire  brushes ; 
the   latter   alone   shall   not   be    considered   sufficient.     Each   such 
surface  shall  then  receive  one  full  coat  of  Durable  Metal  Coating, 
made  by  Edward  Smith  &  Co.,  of  45  Broadway,  New  York. 

The  wire  brush  is  an  efficient  means  of  getting  rid  of  loose 
scale  and  dirt;  but  it  is  practically  worthless  for  removing  thick 
rust  or  anything  which  adheres  closely.  Much  of  such  material 
may  be  removed  by  steel  scrapers;  but  deeply  corroded  spots 
should  be  thoroughly  cleaned  out  with  a  chisel,  and  then  well 
brushed.  These  crevices  are  hereafter  to  be  inaccessible;  and 
they  are  subject  to  the  most  dangerous  corrosion,  because  rust- 
ing at  such  places  impairs  not  only  the  strength,  but  also  the 
stiffness,  of  the  structure — a  matter  of  much  importance.  These 
joints  therefore  deserve  more  care  than  any  other  part. 

II.  Shop-marks   shall  be   compact  and   shall  not   cover  more 
surface  than  the  inspector  directs,  the  intent  being  to  have  the 
surface  occupied  by  such  shop-marks  as  small  as  possible. 

III.  After  assembling,  the  whole  of  the  metal  surfaces  shall  be 
thoroughly  cleaned  in  the  manner  described  in  the  first  section,  and 
shall  then  receive  one  full  coat  of  said  Durable  Metal  Coating,  except 
planed  and  turned  surfaces  and  shop-marks;    and  all  planed  and 
turned  surfaces  shall  be  coated  with  Vacuum  Flushing  Oil  and 
shall  be  kept  so  coated  until  they  are  erected  in  place;    and  all 
small  cavities  which  will  hereafter  be  inaccessible  shall  be  filled 
with  a  mixture  of  one  part  of  Portland  cement  and  three  parts 
of  clean  sand,  with  a  proper  proportion  of  water. 

Many  engineers  are  in  the  habit  of  specifying  a  coat  of  either 
raw  or  boiled  linseed-oil  at  the  shop,  instead  of  a  shop  coat  of 

45 


paint.  The  advantages  claimed  for  a  shop  coat  of  oil  are,  first, 
it  facilitates  inspection,  as  the  oil  is  transparent;  second,  it  makes 
an  extra  coat;  third,  the  paint  is  likely  to  be  more  carefully 
applied  if  used  at  the  place  of  erection.  Doubtless  these  con- 
siderations are  entitled  to  some  weight;  but  many  of  the  best 
engineers  practice  shop-painting,  which  indicates  that  inspection 
can  be  carried  on  efficiently  after  the  first  coat  of  paint  has  been 
applied;  and  at  many  shops  very  excellent  painting  is  done, 
while  the  contractor  who  does  the  erecting  is,  so  far  as  my  obser- 
vation goes,  extremely  indifferent  to  the  paint  question.  When 
it  comes  to  the  matter  of  architectural  ironwork,  we  might  as 
well  give  up  the  idea  of  having  two  coats  of  paint  applied  during 


Thirty-eight-inch  riveted  steel  pipe,  Rochester,  N.  Y.,  1893. 

Sabin  Pipe  Coating. 


Coated  with 


erection;  it  takes  too  much  time,  and  delay  is  a  word  not  in  the 
contractor's  vocabulary  when  paint  is  concerned.  But  another 
and  more  important  matter  is  this:  If  we  apply  a  coat  of  raw 
linseed-oil  we  must  allow  about  a  week  for  it  to  dry,  and  it  cer- 
tainly ought  to  be  kept  all  this  time  under  cover,  for  fresh  oil 
will  wash  off  to  a  considerable  extent  if  exposed  to  rain.  If,  on 
the  other  hand,  we  use  boiled  oil,  we  will  have  it  dry  in  twenty- 
four  hours;  but  boiled  oil  is  much  less  durable  than  raw,  and 
as  this  is  the  foundation  coat  it  is  of  the  highest  importance  that 
it  should  be  as  durable  as  possible;  and  it  is  much  more  difficult 
to  detect  impurities  in  boiled  than  in  raw  oil.  Further,  there 
has  grown  up  among  the  steel  men  a  belief  that  the  shop  coat  of 


oil  is  only  for  protection  during  shipment,  and  with  this  has  come 
the  practice  of  applying  a  cheap  and  worse  than  worthless  sub- 
stitute for  linseed-oil,  composed  chiefly  of  mineral  oil,  some- 
times further  adulterated  with  rosin.  This  oil  will  penetrate 
the  paint  which  is  put  over  it,  and  as  the  film  of  oil  is  about  half 
as  thick  as  the  coat  of  paint  it  is  equivalent  to  thinning  the  latter 
with  half  its  volume  of  very  deleterious  and  injurious  matter.  It 
is  then  a  question  not  how  much  good,  but  how  little  harm  does 
the  shop  coat  of  oil  do.  I  have  no  doubt  that  often  a  good  paint 
has  been  a  failure  because  of  the  shop  coat  of  oil.  And  if  the 
shop  manager  cannot  be  trusted  to  apply  a  shop  coat  of  paint 
I  would  certainly  be  afraid  of  the  oil  he  would  use. 

It  is  worthy  of  note  that  there  is  good  authority  for  the  follow- 
ing procedure  in  bridge  work :  A  shop  coat  of  the  best  raw  linseed- 
oil  is  applied,  and  the  work  is  then  erected  and  allowed  to  stand 
one  to  six  months,  until  the  oil  is  supposed  to  have  thoroughly 
penetrated  and  with  the  aid  of  the  weather  loosened  the  scale. 

The  whole  surface  is  then  very  thoroughly  cleaned  (as  in 
Section  I)  and  given  two  coats  of  paint.  It  is  claimed  that  by 
this  means  the  mill  scale  is  well  removed,  while  rusting  has  been 
avoided.  There  are  reasons  for  thinking  this  good  practice, 
but  it  involves  watchful  care  and  thorough  work. 

If  it  is  determined  to  use  oil,  the  following  specification  is 
recommended : 

The  oil  used  for  this  purpose  shall  be  raw  linseed-oil  of  the 
best  quality;  shall  be  permanently  clear  and  settled  by  aging 
or  storage  for  not  less  than  thirty  days ;  free  from  rosin  as  well  as 
mineral-,  fish-,  and  cottonseed-oils,  or  any  other  impurities;  shall 
contain  no  benzine,  turpentine,  or  other  solvent,  nor  any  lead 
or  manganese  compounds;  it  shall  be  purchased  directly  from 
some  reputable  manufacturer  of  linseed-oil,  and  each  shipment 
shall  be  accompanied  by  a  signed  statement  from  the  manufac- 
turer saying  that  he  has,  at  that  time,  shipped  a  specified  amount 
of  pure  raw  linseed-oil  of  the  best  quality ;  and  it  shall  be  brought 
on  the  premises  where  it  is  to  be  used  in  the  manfacturer's  sealed 
packages,  which  shall  be  opened  in  the  presence  of  the  inspector, 
who  may  then  and  at  any  subsequent  time  take  samples  for  exam- 
ination or  analysis ;  and  in  case  any  analysis  made  by  direction 
of  the  chief  engineer  shows  impurity,  adulteration,  or  substitu- 
tion in  this  material,  the  contractor  shall  pay  all  the  costs  of 
such  analysis,  and  shall  moreover  thoroughly  clean  off  all  metal 
coated  with  such  impure  or  unauthorized  oil  and  recoat  it  to  the 
satisfaction  of  the  inspector.  And  the  contractor  shall  upon 

47 


demand  exhibit  to  the  engineer  or  the  authorized  inspector  the 

bills  and  statements  from  the  manufacturer  showing  the  amounts 

of  oil  purchased. 

In  case  boiled 'oil  is  to  be  used  the  word  "  boiled  "  would  be 

,      substituted    for    "  raw  "  in   the  foregoing,  and 

omit    "nor     any     lead     or      manganese     com- 
pounds." 

But  the  writer  of  this  is  of  the  opinion  that 
a  shop  coat  of  oil  is  in  most  cases  a  useless 
expense  (which  might  far  better  be  applied  to 
a  striping  coat),  and  in  a  large  proportion  of 
cases  a  positive  and  great  injury.  Vacuum 
flushing  oil  is  a  very  heavy  mineral  oil,  about 
as  heavy  as  an  oil  for  wagon  axles,  and  has 
been  successfully  used  for  a  long  time.  It 
appears  to  be  much  better  than  the  usual 
mixture  of  white  lead  and  tallow,  which  is  not 
very  satisfactory.  It  is  not  expensive. 

"  All  small  cavities."  It  is  not  proposed, 
for  example,  to  fill  hollow  columns  in  this  way. 
Large  cavities  which  are  liable  to  be  wet 
should  be  drained;  but  this  is  not  a  matter  of 
painting. 


Unlined  steel  stack, 
310  feet  high,  of 
the  Nichols  Che- 
mical Co.,  Laurel 
Hill,  N.  Y.  City. 
This  has  stood 
six  years,  paint- 
ed on  erection 
with  Durable 
Metal  Coating 
inside  and  out- 
side, without  re- 
painting. 


IV.  The  metal  shall  not  be  exposed  to  the 
weather  nor  loaded  for  shipment  until  in  the 
opinion  of  the  inspector  the  paint  is  sufficiently 
dry.  At  no  time  after  the  application  of  the 
first  coat  of  paint  shall  the  pieces  of  iron  or 
steel  be  laid  on  the  ground,  but  shall  be  laid  on 
skids  or  trestles ;  and  in  all  handling  and  loading 
or  unloading  of  the  same  care  shall  be  taken 
to  avoid  scraping  off  the  preservative  coating; 

and  in   transportation   care   shall   be   taken  to  avoid  nesting  the 

pieces  except  with  packing  material  between  them. 


This  section  calls  for  shop  painting  to  be  done  under  cover. 
This  is  probably  the  most  radical  reform  called  for  in  these  speci- 
fications. Few  shops  have  a  paint-shop  where  such  work  may 
be  done;  but  while  no  serious  objection  can  be  raised  to  painting 
out-of-doors  in  dry,  warm  weather,  it  must  be  remembered  that 
this  kind  of  work  is  going  on  all  the  year  round,  and  that  during 
a  large  part  of  the  time  the  weather  is  such  that  it  is  impossible 

48 


to  do  good  work  outside.  It  seems  to  the  writer  that  if  this 
single  reform  can  be  enforced,  as  it  is  in  all  other  kinds  of  paint - 
ing>  a  great  advance  will  be  made  in  the  matter  of  preserving 
steel  from  corrosion. 

Incidentally  it  has  the  effect  of  making  the  painting  a  dis- 
tinct step  in  the  •  shop  work,  and  recognizing  paint  as  proper 
engineering  material.  The  rest  of  the  section  is  of  the  same 
tenor,  and  will  be  found  difficult  to  enforce,  not  because  it  involves 
any  hardship  or  much  expense  to  the  contractor,  but  because 
steel  is  handled  in  a  slovenly  and  careless  manner,  being  usually 
thrown  off  wagons  or  cars  into  the  mud;  and  inspectors  have 
really  very  great  difficulty  to  get  the  mud  cleaned  off,  or  even 
to  have  a  pretence  made  of  cleaning  it  off,  before  the  second  coat 
of  paint  is  applied.  The  reform  needed  is  a  change  of  the  spirit 
in  which  the  work  is  done,  and  must  lead  to  a  recognition  by  all, 
from  the  owner  to  the  humblest  laborer,  of  the  fact  that  steel 
is  a  perishable  material  the  preservation  of  which  is  a  matter 
of  serious  and  constant  importance. 

V.  After  erection  the  work  shall  be  carefully  inspected,  and  if 
there  are  any  rusty  spots  these  shall  be  thoroughly  cleaned,  and 
all  such  places  and  also  all  places 
where  the  paint  has  been  rubbed 
off  shall  receive  a  coat  of  Edward 
Smith  &  Co.'s  Durable  Metal  Coat- 
ing; and  all  exposed  edges  and 
angles  shall  receive  an  extra  striping 
coat  of  the  same,  covering  the  edge 
and  the  adjacent  surface  one  or  two 
inches  from  the  edge  on  each  side ; 
all  rivet-  and  bolt-heads  and  nuts 
shall  also  receive  an  extra  coat; 
after  this  has  become  dry,  the  whole 
surface,  having  previously  been 
thoroughly  cleaned  from  dirt,  shall 
receive  another  full  coat  of  said 
Durable  Metal  Coating. 


Steel  stack,  200  feet  high,  of  the 
Philadelphia  Smelter,  Pueblo, 
Colo.  Painted  with  Durable 
Metal  Coating. 


VI.  In  no  case  shall  a  second  or 
third  coat  of  paint  be  applied  until 
the  previous  one  is  entirely  dry. 

It  is  proper  at  this  point  to  call  attention  to  the  fact  that 
some  engineers  specify  that  successive  coats  of  paint  shall  differ 

49 


in  color;  some  advise  this  on  the  ground  that  it  makes  it  easier 
for  the  workmen  to  see  if  they  are  missing  any  places,  and  any- 
thing which  makes  painting  easier  is  likely  to  be  advantageous; 
others  say  it  facilitates  inspection  and  enables  the  engineer  to 
find  out  for  himself  if  the  required  number  of  coats  has  been 
applied.  On  the  other  hand,  some  say  there  is  no  difficulty  in 
distinguishing  fresh  paint  from  that  a  day  or  two  old — that,  in 
fact,  any  inspection  worthy  of  the  name  will  determine  whether 
the  work  is  properly  done  without  regard  to  this,  while  com- 
petent inspection  of  bridges  cannot  be  done  from  the  platform  of 
a  railroad  car.  Some  of  the  most  experienced  and  careful 
engineers  specify  paints  of  different  colors  for  different  coats, 
but  others  of  equal  standing  do  not  approve  of  it ;  as  a  result  of 
extended  personal  inquiry  I  am  satisfied  that  a  great  majority 
belong  to  the  latter  class,  and  as  I  myself  hold  this  opinion  I  have 
not  specified  such  difference  in  colors,  but  only  call  attention 
to  the  matter,  so  that  those  who  wish  may  insert  an  article  to 
that  effect. 

VII.  During  erection  any  small  cavities  which  will  hereafter 
be  inaccessible  shall  be  filled  as  provided  in  Section  III. 

VIII.  All  Durable  Metal  Coating  used  for  this  work  shall  be 
purchased  directly  from  the  manufacturer  or  his  authorized  agent, 
and  each  shipment  shall  be  accompanied  by  a  signed  certificate 
from  the  manufacturer  or  such  agent,  stating  that  he  has,  at  that 
time,  shipped  a  specified  amount  of  the  Durable  Metal  Coating; 
and  all  Durable  Metal  Coating  shall  be  brought  on  to  the  premises 
where  it  is  to  be  used  in  the  manufacturer's  sealed  packages,  which 
shall  be  opened  in  the  presence  of  the  inspector,  who  may  then, 
and  at  any  subsequent    time,   take    samples  for  examination   or 
analysis;    and  in  case  any  analysis  made  by  direction  of  the  chief 
engineer    shows    impurity,   adulteration,  or    substitution    in    these 
specified  materials,  the  contractor  shall  pay  all  the  costs  cf  such 
analysis,  and  shall  moreover  thoroughly  clean  off  all  metal  coated 
with  such  impure  or  unauthorized  material  and  shall  repaint  it 
to  the  satisfaction  of  the  inspector.     And  the  contractor  shall,  upon 
demand,   exhibit  to  the  engineer  or  inspector  the  bills  from  the 
manufacturers  or  their  agents,   showing  the   amount   cf  Durable 
Metal  Coating  purchased,  and  also  the  certificates  spoken  of  in  this 
section;    and  the  Durable  Metal  Coating  shall  not  be  thinned  with 
anything  whatsoever,  nor  shall  any  turpentine  or  benzine  be  allowed 
upon  the  premises  for  any  purpose,  except  by  permission  of  the 
inspector  and  in  such  quantity  as  he  may  allow. 


IX.  The  inspector  shall  be  notified  when  any  painting  is  to  be 
done,  and  no  such  work  is  to  be  done  until  the  inspector  has  approved 
the  surface  to  which  it  is  to  be  applied;    and  the  contractor  shall 
furnish  all  facilities  for  inspection  and  for  necessary  marking  by 
the  inspector,  and  all  materials,  such  as  paint,  brushes,  etc.,  for 
such   marking.     No    such   inspection    or   marking   shall   be    done 
except  by  the  engineer  or  his  authorized  inspector. 

X.  In  no  case  shall  any  paint  be  applied  out-of-doors  in  freezing, 
rainy,  or  misty  weather,  and  all  surfaces  to  which  paint  is  to  be 
applied  must  be  at  the  time  dry  and  clean;   and  all  work  must  be 
done   in   a  thorough,   neat,   and  workmanlike   manner.     If  it  is 
necessary  in  cool  weather  to  thin  the  paint,  this  may  be  done  only 
by  heating  it,  and  this  may  be  required  by  the  inspector. 

XI.  The  foregoing  specifications  shall  be  accepted  and  carried 
out  faithfully  in  every  particular  and  shall  not  be  construed  accord- 
ing to  any  prevalent  practice  not  in  full  accord  therewith. 

5' 


•_d    o 
7D     w 


IV. 
SOME  ANTI-CORROSIVE  COATINGS. 

Edward  Smith  &  Company  manufacture  all  lines  of  such 
varnishes  as  are  used  in  structural  work,  as  well  as  varnishes 
for  carriages,  railway  coaches,  yachts,  and  the  like;  but  besides 
these  they  have  for  many  years  made  a  special  business  of  making 
protective  coatings  to  prevent  the  corrosion  of  iron  and  steel 
in  bridges,  train-sheds,  water-tanks,  and  mains,  and  in  fact  all 
work  where  metal  is  exposed  to  risk  of  corrosion.  There  is  no 
one  material  which  is  best  for  all  places ;  and  they  maintain  a 
chemical  and  testing  laboratory,  well  equipped,  and  their  officers 
are  in  a  position  to  offer  intelligent  and  expert  advice  on  almost 
all  questions  of  this  sort,  and  to  make  special  preparations  for 
unusual  conditions.  This  is  now  so  well  known  that  they  are 
consulted  as  experts  by  many  engineers  of  the  highest  repute. 

Durable  Metal  Coating. 

This  is  the  best  known  and  most  popular  of  these  anti-rust 
preparations  made  by  this  company,  and  the  following  is  a  brief 
account  of  its  qualities  and  uses. 

It  is  an  oleo-resinous  varnish,  of  the  highest  durability  and 
elasticity;  it  is  black  in  color.  When  dry  it  is  not  affected  by 
nor  does  it  affect  any  paint  put  on  over  it ;  it  is  therefore  practic- 
able to  use  paint  of  any  color  as  a  finishing  coat  if  desired.  Two 
coats  of  white  zinc  or  white  lead  cover  well,  and  if  the  desired 
color  is  of  a  neutral  or  dark  shade  one  coat  is  often  sufficient. 
If  it  is  desired  to  throw  it  off  color  only  a  little,  the  painter  may 
add  to  it  pigments  either  dry  or  ground  to  a  paste  in  oil;  for 
example,  a  bronze-green  suitable  for  certain  ornamental  ironwork 
in^parks,  etc.,  may  be  had  by  adding  a  little  chrome  green,  or 
olive  by  medium  chrome  yellow.  For  engineers  who  desire  to 
use  different  colors  in  successive  coats,  we  will  make  it  in  dark 
green,  chocolate-brown,  or  olive,  if  the  order  is  of  considerable 

53 


amount.  Used  without  the  addition  of  any  color  it  gives  a  very 
handsome  and  permanent  black  finish  to  iron  and  steel,  which  is 
generally  liked,  black  being  commonly  regarded  as  a  natural 


Steel  beams  (painted  with  Durable  Metal  Coating)  of  the  Stadium,  Harvard 
University.      Prof.  L.  J.  Johnson,  engineer. 

and    proper    color     for     iron.       Most     of     it    is    used    in    this 
way. 

One  gallon  will  cover  from  300  to  400  square  feet,  according 
to  the  character  of  the  surface.  If  the  latter  is  very  rough,  owing 
to  corrosion,  it  may  not  cover  more  than  250  square  feet  the 
first  coat,  because  in  that  case  it  acts  as  a  filler,  but  it  will  cover 
more  than  300  square  feet  for  the  second  coat.  There  is  not  a 
great  difference  in  the  amount  of  surface  covered  by  different 
paints,  if  the  surfaces  are  alike  in  material  and  smoothness,  because 
all  paints  and  varnishes  are  made  up  to  a  certain  conventional 
standard  of  viscosity,  suitable  for  working  with  the  brush;  and 
any  paint  or  varnish  made  for  general  use  must  be  modified  if 
used  in  an  unusual  way,  if  applied  by  dipping,  for  example;  and 
a  skilful  painter  may  make  any  structural  paint  cover  500  or 
600  square  feet  by  spending  enough  labor  on  it  brushing  it  out 
thin;  but  this  is  practically  not  done  because  the  labor  costs 
more  than  the  paint,  and  theoretically  it  never  should  be  done, 
because  such  a  coating  is  too  thin  to  afford  sufficient  protection. 
For  decorative  effect  thin  coats  are  best;  for  protection  they 
should  be  as  thick  as  can  be  applied  uniformly  and  lie  smoothly. 

54 


Paints  may  be  made  to  cover  more  surface  if  they  are  made  very 
thin  with  benzine  or  turpentine,  but  are  then  of  little  value. 

Durable  Metal  Coating  is  supplied  ready  to  use,  and  must 
not  on  any  account  be  thinned  with  anything.  It  is  a  perfect 
liquid,  containing  no  pigment,  does  not  require  stirring,  and 
can  be  used  to  the  last  drop  in  the  barrel.  It  contains  no  coal- 
tar,  no  naphtha  or  other  coal-tar  product;  no  benzine  or  any 
petroleum  derivative;  no  rosin  or  rosin-oil;  no  materials  but 
the  purest  and  best  for  the  purposes  for  which  it  is  made.  It  is 
usually  sold  in  barrels,  but  will  be  put  up  in  packages  of  any 
size,  smaller  packages  being  charged  extra  at  the  usual  rates. 
It  may  be  shipped  to  India  and  other  hot  countries  in  ico-gallon 
drums,  or  in  sealed  cans,  if  barrels  are  not  thought  suitable  on 
account  of  the  climate. 

It  is  not  necessary  to  have  skilled  labor  for  its  application, 
unless  it  is  to  be  used  as  an  ornamental  coating,  as  it  sometimes 
is.  If  it  is  necessary  (as  often  happens)  to  use  it  out-of-doors 
in  cold  weather,  it  mav  be  heated  to  make  it  more  fluid.  Thou- 


Pierce  Hall  (Engineering  building),  Harvard  University.      Steel  framework 
painted  with  Durable  Metal  Coating.     Prof.  L.  J.  Johnson,  engineer. 


sands  of  gallons  have  thus  been  treated  by  the  Northern  Pacific 
Railroad  Company  and  others;  as  it  contains  no  benzine  it  is 
perfectly  safe  to  heat  it  to  as  high  a  temperature  as  it  is  reason- 

55 


able  to  subject  the  bristle  brushes  which  are  used  in   applying 
it — say  to  150°  F. 

It  is  commonly  estimated  to  require  about  thirty-six  hours 
to  dry  so  that  it  may  be  handled,  and  from  three  or  four  days 
to  two  weeks  for  it  to  dry  through.  It  does,  however,  continue 
to  harden  for  at  least  two  weeks,  and  in  cold  or  wet  weather  it 
may  require  more  than  thirty-six  hours  before  it  may  be  handled, 
while  in  hot,  dry  weather  it  has  been  known  to  dry  to  this  extent 
in  from  eight  to  twelve  hours. 


Pierce   Building   (for   engineering),    Mass.    Institute   of   Technology, 
framework  painted  with  Durable  Metal  Coating. 


Steel 


A  second  coat  should  not  be  applied  in  less  than  three  days 
and  a  week  or  ten  days  is  much  better.  In  fact,  in  bridgework 
it  is  good  practice  to  allow  two  to  four  weeks  between  coats,  with 
any  kind  of  paint.  But  if  it  can  be  dried  by  heat,  as  is  the  case 
with  much  .ornamental  ironwork  and  with  small  objects  gen- 
erally, it  will  dry  in  two  or  three  hours  at  200°  to  250°.  It  dries 
by  oxidation,  and  heat  accelerates  this  process.  If  it  is  impossible 
to  allow  a  sufficient  time  between  coats,  we  advise  the  use  of  our 
Ebonite  varnish  for  a  first  coat,  which*  dries  much  more  quickly. 

We  do  not  give  any  guarantee'  of  performance.  No  reputable 
manufacturer  can  afford  to  do  this,  not  knowing  the  character 
of  the  surtace  to  which  the  paint  is  to  be  applied,  the  intelligence 

56 


of  t he-man  who  applies  it,  the  treatment  it  is  to  receive,  or  any 
of  the  many  things  which  affect  the  durability  of  a  paint  or  var- 
nish. If  the  reader  will  take  the  trouble  to  look  up  with  the 
aid  of  any  of  the  commercial  agencies  the  standing  ot  the  paint 
manufacturers,  he  will  find  that  no  one  having  a  considerable 
rating  offers  a  guarantee  which  amounts  to  anything;  some- 
times, to  effect  a  sale,  a  guarantee  is  offered,  but  careful  exam- 
ination will  always  show  that  it  is  so  protected  by  restrictions 
that  no  real  guarantee  is  given.  In  general,  no  paint  guarantee 
is^good  for  anything  except  a  contract  to  keep  a  structure  painted 
a  specified  time  for  a  certain  sum  of  money.  The  curious  inves- 
tigator will  also  notice  that  some  of  the  concerns  which  give 
recommendations  for  certain  paints  are  not  mentioned  in  the 
books  of  the  commercial  agencies;  and  that  sometimes  pictures 
of  structures  are  sent  out  with  advertising  matter  which  were 
not  painted  with  the  advertiser's  material;  it  is  not  expressly 
claimed  that  they  were  so  painted,  but  the  obvious  intention 
is  to  make  the  public  believe  it.  There  are  plenty  of  reputable 
paint  manufacturers,  and  it  is  not  necessary  to  do  business  with 
tricksters. 

Edward  Smith  &  Co.  wish  to  call  attention,  especially  on 
the  part  of  architects  and  engineers,  to  the  fact  that  it  is  desir^ 
able  to  specify  "  Durable  Metal  Coating  made  by  Edward 
Smith  &  Co.  of  45  Broadway,  N.  Y.,"  because  at  least  one  con- 
cern has  sent  its  agents  around  to  our  customers  offering  to  sell 
them  a  paint  under  the  same  name  and  guaranteed  "  equal  to 
Smith's,"  at  prices  varying  from  90  cents  or  $1.00  per  gallon, 
in  the  case  of  architects,  to  as  low  as  12^  cents  a  gallon  to  the 
large  steel  companies.  This  paint  was  not  worth  12^  cents  per 
gallon,  and  will  not  be  satisfactory  to  people  who  want  Edward 
Smith  &  Co.'s  goods;  and  it  has  been  used  when  the  latter  were 
specified.  Therefore  take  warning. 

While  we  strongly  recommend  thorough  cleaning  of  all  sur- 
faces which  are  to  be  painted,  we  do  not  wish  to  be  understood 
as  meaning  that  our  paint  cannot  be  applied  to  any  but  a  clean 
metallic  surface.  It  has  been  and  is  constantly  being  used  as  a 
protective  coating  over  red  lead  (on  the  ground  that  the  good 
qualities  of  the  latter  depend  on  its  protection  from  the  atmos- 
sphere);  and  there  is  no  serious  objection  to  using  it  over  old 
paint  which  is  in  good  condition  and  adheres  well. 

Durable  Metal  Coating  has  a  considerable  use  in  railroad 
work.  The  bridge  at  Eagle  Bridge,  N.  Y.,  consisting  of  two 
plate-girder  spans  aggregating  about  200  feet  in  length,  was 

57 


painted  with  two  coats  of  this  material  when  erected,  in  1893; 
it  gets  all  the  refrigerator  drip  from  the  east-bound  trains  of 
the  Fitchburg  R.R. ;  it  has  not  [been  repainted,  even  in  part, 


Eagle  Bridge,  N.  Y.     Painted  with  Durable  Metal  Coating. 

and  is  now  (1905)  in  excellent  condition.  Now,  it  is  impossible 
to  make  a  paint  which  will  stand  refrigerator  drip  ten  or  twelve 
years  unless  it  is  carefully  and  thoroughly  applied  to  new  or 
clean  metal,  under  favorable  conditions;  and  any  good  paint 
thus  applied  will  give  better  than  average  results ;  but  it  is  beyond 
question  that  a  paint  which  has  stood  as  long  as  this,  and  is  appar- 
ently good  for  many  years  yet,  must  be  of  exceptional  quality. 
_JTo  take  another  case:  In  1896  the  large  train-shed  of  the 
Illinois  Central  R.R.  in  Chicago  (which  is  also  used  by  the  Michi- 
gan Central)  was  -painted  inside  with  Durable  Metal  Coating, 
two  coats.  This  was  a  repainting  job;  the  paint  originally  used 
Kkd  perished,  and  was  thoroughly  cleaned  off  by  scraping  and 
wire-brushing  before  the  application  of  our  material.  This  stood 
all  right  without  repairs  for  six  years ;  at  the  end  of  which  time 
the  exterior  of  the  shed  was  being  painted  with  Durable  Metal 
Coating,  and  a  third  coat  was  then  put  on  the  interior;  no  scrap- 
ing was  necessary,  only  ordinary  cleaning  with  brushes;  the 
1*896  paint  was  all  right,  but  the  additional  coat  was  applied 
over  the  others.  It  is  now  in  excellent  condition.  This  is  both  a 
terminal-  and  a  through- train  shed,  670  by  140  feet,  and  the  test 
is  a  severe  one.  Its  fine  condition  was  one  reason  why  the  Chicago 

58 


&  Northwestern  R.R.  painted  their  large  train-shed  at  their 
main  station  (Wells  Street)  in  Chicago,  in  1903,  with  Durable 
Metal  Coating.  This  is  the  only  C.  &  N.  W.  structure  of  con- 
siderable importance,  so  far  as  known  to  the  writer,  which  is 
painted  with  anything  but  the  C.  &  N.  W.  standard  paint  made 
in  the  shops  of  the  railroad  company;  it  was  adopted  without 
solicitation,  and  after  careful  investigation  by  the  officials  in 
charge  of  the  work. 

The  Illinois  Central  has  used  thousands  of  gallons  of  Durable 
Metal  Coating  for  bridge  work  and  are  still  using  it,  especially 
for  first-coat  work,  at  the  bridge  shops.  A  large  amount  has 
been  used  on  the  Northern  Pacific  and  other  roads  in  the  North- 
west; this  was  probably  the  reason  that  caused  the  Canadian 
Pacific  R.R.  to  use  it  on  their  train-shed  at  Montreal  and  else- 
where; they  were  never  asked  to  use  it. 

Another  thing  for  which  Durable  Metal  Coating  is  used  is  for 
painting  wire  cables  of  electric  wires,  such  as  are  used  for  block- 
signal  lines  and  the  like.  The  New  York  Central  R.R.  has  used 


Highway  Bridge  at  Albany,  N.  Y.     Painted  with  Durable  Metal  Coating. 
Stowell  and  Cunningham,  designers. 

some  thousands  of  gallons  for  this  purpose;  and  the  Western 
Union  Telegraph  Co.  has  used  considerable  quantities  of  it  for 
many  years.  It  is  also  used  by  the  Postal  Telegraph  Co.  on 

59 


cables  and  other  work.  It  has  proved  satisfactory  for  painting 
all  sorts  of  exposed  work  for  telegraphs  and  electric  light  and 
power,  such  as  metallic  poles,  cross-arms,  and  the  like.  For  all 


Train-shed  of  the  Wells  Street  Depot  of  the  C.  &  N.  W.  R.R.,  Chicago. 
Painted,  1903,  with  Durable  Metal  Coating.  E.  C.  Carter,  Ch.  Eng. 
W.  H.  Finley,  Prin.  Asst.  Eng. 


such  uses  it  is  better  than  an  oil  paint,  because,  for  one  thing, 
it  contains  no  pigment;  most  sorts  of  pigment  are  conductors 
of  electricity,  and  the  better  insulator  a  coating  is  the  less  likely 
is  rusting  to  be  set  up,  particularly  on  metal  which  is  more  or 
less  charged  with  electricity.  The  metal  work  of  steel-frame 
buildings  is  essentially  similar  to  bridge  work,  and  many  of  the 
finest  structures  of  this  sort  in  the  country  have  been  protected 
with  this  coating.  If  it  is  necessary  to  use  a  more  rapid  drying 
material  our  coating  called  Ebonite  is  recommended. 

For  painting  water-towers  and  tanks  for  drinking-water  it 
is  unequalled.  It  is  generally  admitted  that^lead  paints  are  not 
suited  for  such  uses,  because  of  the  possibility  that  the  lead  may 
be  dissolved  in  the  water;  in  this  varnish  there  is  nothing  which 
can  be  dissolved,  nor  that  would  be  objectionable  if  it  were  dis- 

60 


solved.  It  is  particularly  liked  for  painting  tanks  for  water 
on  ships  and  yachts;  it  never  becomes  loosened  by  the  vibra- 
tion of  the  boat.  In  his  annual  address  one  of  the  presidents 
of  the  New  England  Water  Works  Association  mentioned  it  as 
the  best  coating  for  water-towers;  a  great  many  of  them  have 
been  painted  with.it,  and  we  have  yet  to  have  the  first  complaint. 
It  has  also  been  used  for  ten  years  on  both  steel  and  cast-iron 
water-mains,  with  satisfactory  results. 

It  is  well  adapted  for  painting  metal  roofs.  It  is  well  known 
that  new  tin  or  galvanized-iron  roofs  are  difficult  to  paint;  this  is 
because  in  making  the  sheets  of  coated  metal  they  receive  a  closely 
adherent  thin  film  of  such  sort  that  paint  of  any  kind  will  not 
adhere  to  it;  the  remedy  is  to  thoroughly  clean  by  scrubbing 
with  soap  and  water,  and  if  greasy  by  rubbing  with  coarse  cloths 
wet  in  benzine.  If  the  roof  is  very  thoroughly  cleaned  any  paint 
will  stick  on  it.  Durable  Metal  Coating  is  extremely  water-proof 
and  permanently  elastic,  and  is  in  every  way  a  good  roof  paint. 


Windsor  Street  Station,  Montreal,  of  the  Canadian  Pacific  R.R. 
painted  with  Durable  Metal  Coating. 


Train-shed 


As  it  stands  high  temperatures  well,  it  is  suitable  for  painting 
smoke-stacks,  steam-pipes,  and  the  like.  No  organic  material 
will  stand  a  heat  much  in  excess  of  400°  F.;  beyond  this  it  is  more 

61 


or  less  rapidly  burned  off;  but  this  coating  bakes  to  a  sort  of 
enamel  with  any  reasonable  temperature,  and  is  a  very  per- 
fect coating.  It  is  not  affected  by  acid  gases  and  is  extensively 


Eye-bar  chains  in  the  anchorages  of  the  Williamsburg  Bridge.      Protected 
with  Ebonite  Varnish. 


used  about  chemical  works;  the  chief  cause  of  deterioration  of 
paint  in  such  places  is  the  action  of  acids  pn  the  pigment  which 
constitutes  a  large  part  of  an  ordinary  paint;  as  this  does  not 
contain  any  pigment  it  is  not  affected. 

It  stands  well  over  sea- water,  not  being  readily  affected  by 
the  spray;  but  we  do  not  recommend  it  for  use  under  the  sur- 
face of  sea-water.  If  Durable  Metal  Coating  is  to  be  used  on 
decorative  work,  it  must  be  brushed  out  thin;  otherwise  it  will 
wrinkle.  If  it  is  brushed  out  thin  it  dries  more  rapidly,  which 
is  an  advantage  for  this  kind  of  work;  but  enough  coats  must 
be  applied  to  make  a  substantial  film.  If  treated  intelligently 
in  this  way  it  has  been  a  most  satisfactory  material;  for  example, 
it  was  thus  used  on  the  ornamental  ironwork  of  the  Delmonico 
building,  by  John  Williams,  well  known  as  a  leading  manufac- 
turer of  bronze  and  iron  ornamental  work,  in  whose  shops  it  has 
long  been  used.  But  it  must  not  be  forgotten  that  a  very  thin 

62 


coat   of  the   best  material  will  not   long  stand   exposure   to   the 
weather;    enough  must  be  used  to  ensure  protection. 

Ebonite  Varnish. — This  is  a  preparation  which  differs  from 
Durable  Metal  Coating  by  containing  less  oil  in  proportion  to 
the  resinous  material;  it  dries  more  rapidly  on  that  account, 
and  its  drying  is  greatly  increased  by  the  fact  that  as  it  contains 
less  oil  and  would  therefore  be  less  fluid  it  is  necessary  to  make 
it  contain  more  turpentine;  and  a  large  proportion  of  turpen- 
tine makes  a  varnish  dry  quickly.  It  is  subject  to  the  objec- 
tion that  it  makes  a  thinner  film  than  the  other;  but  besides  the 
advantage  of  quicker  drying  it  naturally  resists  alkalies  better 
because  of  its  large  proportion  of  resinous  material;  this  latter 
being  unaffected  by  alkali.  Where  the  coating  is  to  be  in  con- 
tact with  hydraulic  cement  this  is  an  important  advantage.  The 
entire  metal  work  in  the  anchorages  of  the  Williamsburg  bridge, 
connecting  New  York  and  Brooklyn,  was  painted  with  several 
coats  of  this  compound;  and  its  good  condition  several  years 


Eye-bar  chains  in  the  anchorages  of  the  Williamsburg  Bridge,  N.  Y.  City. 
Protected  with  Ebonite  Varnish. 

later  was  undoubtedly  one  reason  why  the  equally  important 
task  of  making  a  coating  material  for  the  cables  of  that  great 
engineering  work  was  entrusted  to  our  company. 

63 


Another  instructive  instance  of  its  use  in  contact  with  cement 
is  afforded  by  a  paper  read  before  the  American  Institute  of 
Mining  Engineers  in  February  1904,  describing  the  dust-flues 
at  the  smelter  in  Leadville,  Colo.,  built  in  1898^ and  still  in  good 
condition.  The  engineer  of  construction  said: 

"  In  regard  to  the  effect  of  sulphur  dioxide  and  furnace-gases 
on  the  cement,  I  have  found  that  in  certain  cases  this  is  a  matter 
which  must  be  given  very  careful  attention.  When  there  is 
sufficient  heat  to  prevent  the  existence  of  condensed  moisture 
inside  of  the  flue,  there  is  apparently  no  action  whatever  on  the 
cement,  but  if  the  concrete  is  wet,  it  is  rapidly  rotted  by  these 
gases.  At  points  near  the  furnaces  there  is  generally  sufficient 
heat  not  only  to  prevent  internal  condensation  of  the  aqueous 
vapor  always  present  in  the  gases,  but  also  to  evaporate  water 
from  rain  or  snow  falling  on  the  outside  of  the  flue.  Further 
along  a  point  is  reached  where  rain-water  will  percolate  through 
minute  cracks  caused  by  expansion  and  contraction,  and  reachs  . 
the  interior  even  though  internal  condensation  does  not  occur 
there  in  dry  weather.  From  this  point  to  the  end  of  the  flue 
the  roof  must  be  coated  on  the  outside  with  impervious  ma- 
terial. In  very  long  flues  a  point  may  be  reached  where 
moisture  will  condense  on  the  inside  of  the  walls  in  cold  weather. 
From  this  point  to  the  end  of  the  flue  it  is  essential  to  protect 
the  interior  with  an  acid-resisting  paint,  of  which  two  or  more 
coats  will  be  necessary.  For  the  first  coat  a  material  contain- 
ing little  linseed-oil  is  best,  as  I  am  informed  that  the  lime  in 
the  cement  attacks  the  oil.  For  this  purpose  I  have  used  Ebonite 
varnish,  and  for  the  succeeding  coats,  Durable  Metal  Coating." 

Ebonite  is"  particularly  serviceable  for  work  on  steel-frame 
buildings,  especially  where  haste  is  unavoidable.  It  dries  so 
that  it  may  be  handled  in  a  few  hours,  and  two  coats  may  be 
applied  in  a  day;  but  the  rapidity  of  drying  is  somewhat  more 
apparent  than  real ;  what  really  happens  is  that  it  takes  an  unusu- 
ally hard  preliminary  set,  and  the  final  permanent  drying  is  about 
as  slow  as  that  of  Durable  Metal  Coating.  Having'  had^  rt£  in 
use  about  ten  years,  we  do  not  hesitate  to  recommend  it. 

Edward  Smith  &  Company  have  made  a  great  variety  of  spe- 
cial protective  and  decorative  coatings  for  particular  uses.  For 
instance,  in  a  case  where  it  was  desired  to  paint  a  highway  bridge 
a  certain  color,  they  made  a  varnish  enamel  paint  especially  for  that 
bridge.  This  was  made  with  a  special  varnish,  adapted  to  resist 
the  action  of  the  weather  and  to  protect  the  iron ;  some  varnishes 
do  not  act  well  on  iron,  and  no  ordinary  varnish  will  permanently 


resist  the  weather  in  such  a  place  as  a  bridge  over  sea-water. 
This  was  the  bridge  connecting  the  city  of  Boston  with  Charles- 
town,  the  one  on  which  the  elevated  railway  crosses;  and  it  is 
subjected  to  very  trying  conditions,  being  exposed  to  smoke 
from  tugs  and  other  vessels,  to  fog  and  spray  from  sea-water, 
and  great  extremes  of  rapidly  varying  temperature.  After  five 
or  six  years'  use,  during  which  time  not  the  least  repainting  has 
been  necessary,  the  condition  of  the  surface  is  such  as  to  con- 
stitute the  best  sort  of  a  recommendation  for  the  paint.  This 
is  one  of  the  largest  and  most  important  structures  of  its  kind 
in  the  country;  and  when  we  consider  the  high  grade  of  municipal 
work  done  in  Boston,  the  fact  that  the  coating  is  satisfactory 
to  the  engineers  for  the  city  is  enough  to  recommend  it. 

The  baked  enamel  coating  of  our  invention  which  has  been 
so  successfully  applied  to  pipework  and,  as  described  in  the  first 
part  of  this  book,  to  the  floor  of  the  Williamsburg  bridge,  and 
ihe  special  coating  made  for  the  cables  of  that  structure,  are 
other  instances  of  our  special  work.  It  may  be  confidently  stated 
that  no  other  company  has  done  anything  like  as  much  of  this 
difficult  special  work,  or  has  the  scientific  and  technical  equip- 
ment and  experience  to  successfully  carry  it  out.  This  is  a  con- 
sideration which  should  properly  influence  engineers  and  archi- 
tects in  the  choice  of  material. 

65 


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